refactor: libc - share printf, split the float path, fix relink deps

.gitignore

@@ -16,6 +16,8 @@ programs/obj/
 programs/src/*/obj/
 programs/libs/*/obj/
 programs/lib/libc/liblibc.a
+programs/lib/libc/liblibc-full.a
+programs/lib/libc/obj/libc-merged.o
 programs/lib/libloader/liblibloader.a
 programs/gui/icons/
 CLAUDE.md

programs/GNUmakefile

@@ -105,8 +105,24 @@ lib/bearssl/build/libbearssl.a:
 bearssl: lib/bearssl/build/libbearssl.a
 
 # Build shared libc static library.
-libc:
+#
-	$(MAKE) -C lib/libc
+# The archives and CRT objects get a real file rule, not just the `libc`
+# phony, so that programs can list them as prerequisites and actually relink
+# when libc changes. A phony prerequisite would instead make every program
+# permanently out of date; no prerequisite at all (the old state) both races
+# under -j and silently leaves programs linked against a stale libc.
+# Grouped target (&:, GNU make 4.3+): one sub-make produces all of them.
+LIBC_DIR     := lib/libc
+LIBC_LIB     := $(LIBC_DIR)/liblibc.a
+LIBC_SRCS    := $(wildcard $(LIBC_DIR)/*.c $(LIBC_DIR)/*.h $(LIBC_DIR)/*.S \
+                           $(LIBC_DIR)/crt/*.c) $(LIBC_DIR)/Makefile
+LIBC_OUTPUTS := $(LIBC_LIB) $(LIBC_DIR)/liblibc-full.a \
+                $(LIBC_DIR)/crt1.o $(LIBC_DIR)/crti.o $(LIBC_DIR)/crtn.o
+
+$(LIBC_OUTPUTS) &: $(LIBC_SRCS)
+	$(MAKE) -C $(LIBC_DIR)
+
+libc: $(LIBC_OUTPUTS)
 
 # Build shared TLS helper library.
 tls: bearssl libc
@@ -144,8 +160,8 @@ libjpegwrite: libc
 imageviewer: libc libjpeg
 	$(MAKE) -C src/imageviewer
 
-# Build fontpreview standalone GUI client (no library deps).
+# Build fontpreview standalone GUI client (links libc).
-fontpreview:
+fontpreview: libc
 	$(MAKE) -C src/fontpreview
 
 # Build spreadsheet standalone GUI client (depends on libc and libdialogs).
@@ -271,8 +287,9 @@ mandelbrot: libc
 rpgdemo: libc
 	$(MAKE) -C src/rpgdemo
 
-# Build doom via its own Makefile (depends on libc).
+# Build doom via its own Makefile (depends on libc and the shared-lib loader,
-doom: libc
+# both of which it links).
+doom: libc libloader
 	$(MAKE) -C src/doom
 
 # Build screenshot tool (depends on libc, libjpegwrite, libloader, and libdialogs).
@@ -369,10 +386,10 @@ $(BINDIR)/os/wallpapers/%: $(WPDIR)/%
 	cp $< $@
 
 # Build each system program from its source files.
-$(BINDIR)/os/%.elf: src/%/main.cpp link.ld GNUmakefile
+$(BINDIR)/os/%.elf: src/%/main.cpp link.ld GNUmakefile $(LIBC_LIB)
 	mkdir -p $(BINDIR)/os obj/$*
 	$(CXX) $(CXXFLAGS) -c src/$*/main.cpp -o obj/$*/main.o
-	$(CXX) $(CXXFLAGS) $(LDFLAGS) obj/$*/main.o lib/libc/liblibc.a -o $@
+	$(CXX) $(CXXFLAGS) $(LDFLAGS) obj/$*/main.o $(LIBC_LIB) -o $@
 
 # ============================================================================
 # Native development kit (Montauk SDK): binutils built for MontaukOS
@@ -399,7 +416,10 @@ ifneq ($(wildcard $(NATIVE_BIN)/as),)
 	cp -r include/montauk $(BINDIR)/sdk/include/montauk
 	cp -r include/Api $(BINDIR)/sdk/include/Api
 	cp -r ../kernel/freestnd-cxx-hdrs/x86_64/include/. $(BINDIR)/sdk/include/
-	cp lib/libc/liblibc.a $(BINDIR)/sdk/lib/libc.a
+	# liblibc-full.a, not liblibc.a: on-OS builds cannot pass
+	# -Wl,-u,_pf_putfloat, so the sysroot ships the variant with the printf
+	# float path already bound in. See lib/libc/Makefile.
+	cp lib/libc/liblibc-full.a $(BINDIR)/sdk/lib/libc.a
 	cp lib/libc/crt1.o lib/libc/crti.o lib/libc/crtn.o $(BINDIR)/sdk/lib/
 	ar rcs $(BINDIR)/sdk/lib/libm.a
 	cp ../toolchain/local/x86_64-montauk/lib/libstdc++.a $(BINDIR)/sdk/lib/libstdc++.a

programs/lib/libc/Makefile

@@ -10,9 +10,11 @@ TOOLCHAIN_PREFIX := $(shell cd ../../.. && pwd)/toolchain/local/bin/x86_64-monta
 ifneq ($(wildcard $(TOOLCHAIN_PREFIX)gcc),)
     CC := $(TOOLCHAIN_PREFIX)gcc
     AR := $(TOOLCHAIN_PREFIX)ar
+    LD := $(TOOLCHAIN_PREFIX)ld
 else
     CC := gcc
     AR := ar
+    LD := ld
 endif
 
 # ---- Paths ----
@@ -63,16 +65,25 @@ CRT_CFLAGS := \
 # ---- Target ----
 
 TARGET := liblibc.a
+SDK_TARGET := liblibc-full.a
 CRT_OBJS := crt1.o crti.o crtn.o
 
 .PHONY: all clean
 
-all: $(TARGET) $(CRT_OBJS)
+all: $(TARGET) $(SDK_TARGET) $(CRT_OBJS)
 
-$(TARGET): $(OBJDIR)/libc.o $(ASM_OBJS)
+# printf_float.o is deliberately a SEPARATE archive member: a weak undefined
+# reference does not extract an archive member, so programs that never format
+# a float leave the decimal-conversion and pow/exp/log code behind. Programs
+# that do need %e/%f/%g must link with -Wl,-u,_pf_putfloat to force it in.
+$(TARGET): $(OBJDIR)/libc.o $(OBJDIR)/printf_float.o $(ASM_OBJS)
 	$(AR) rcs $@ $^
 
-$(OBJDIR)/libc.o: libc.c Makefile
+$(OBJDIR)/libc.o: libc.c printf_internal.h Makefile
+	@mkdir -p $(OBJDIR)
+	$(CC) $(CFLAGS) -c $< -o $@
+
+$(OBJDIR)/printf_float.o: printf_float.c printf_internal.h Makefile
 	@mkdir -p $(OBJDIR)
 	$(CC) $(CFLAGS) -c $< -o $@
 
@@ -80,6 +91,17 @@ $(OBJDIR)/setjmp.o: setjmp.S Makefile
 	@mkdir -p $(OBJDIR)
 	$(CC) $(CFLAGS) -c $< -o $@
 
+# Variant shipped in the on-OS sysroots (0:/sdk/lib/libc.a and tcc's), where
+# nobody can pass -Wl,-u,_pf_putfloat by hand. `ld -r` binds vsnprintf's weak
+# reference to the float module at merge time, so %e/%f/%g just work for code
+# compiled ON MontaukOS. Function-level --gc-sections still applies to the
+# rest; only the float path is pinned. Image size is not a concern here.
+$(SDK_TARGET): $(OBJDIR)/libc-merged.o $(ASM_OBJS)
+	$(AR) rcs $@ $^
+
+$(OBJDIR)/libc-merged.o: $(OBJDIR)/libc.o $(OBJDIR)/printf_float.o
+	$(LD) -r -o $@ $(OBJDIR)/libc.o $(OBJDIR)/printf_float.o
+
 crt1.o: $(CRTDIR)/crt1.c Makefile
 	$(CC) $(CRT_CFLAGS) -c $< -o $@
 
@@ -90,4 +112,4 @@ crtn.o: $(CRTDIR)/crtn.c Makefile
 	$(CC) $(CRT_CFLAGS) -c $< -o $@
 
 clean:
-	rm -rf $(OBJDIR) $(TARGET) $(CRT_OBJS)
+	rm -rf $(OBJDIR) $(TARGET) $(SDK_TARGET) $(CRT_OBJS)

programs/lib/libc/libc.c

@@ -1150,13 +1150,17 @@ int system(const char *command) {
    printf family — vsnprintf core
    ======================================================================== */
 
-struct _pf_state {
+#include "printf_internal.h"
-    char *buf;
-    size_t pos;
-    size_t max;
-};
 
-static void _pf_putc(struct _pf_state *st, char c) {
+/* Weak: resolves to 0 unless the program pulls in printf_float.o with
+   -Wl,-u,_pf_putfloat. See the %e/%f/%g case in vsnprintf below. */
+extern __attribute__((weak)) void _pf_putfloat(struct _pf_state *st, double v,
+                                               char conv, int precision,
+                                               int width, char pad,
+                                               int left_align, int plus,
+                                               int space, int alt);
+
+void _pf_putc(struct _pf_state *st, char c) {
     if (st->pos < st->max)
         st->buf[st->pos] = c;
     st->pos++;
@@ -1208,226 +1212,6 @@ static void _pf_putnum(struct _pf_state *st, unsigned long val, int base, int up
         _pf_putc(st, tmp[--i]);
 }
 
-/* Union for double bit manipulation (used by float formatting and math). */
-typedef union { double d; uint64_t u; } _dbl_bits;
-
-/* Base-10 exponent of the leading digit of a positive finite value, i.e. the
-   E such that value = m * 10^E with m in [1, 10). No rounding is applied. */
-static int _pf_exp10(double v) {
-    int E = (int)floor(log10(v));
-    double s = v / pow(10.0, (double)E);
-    if (s >= 10.0) E++;
-    else if (s < 1.0) E--;
-    return E;
-}
-
-/* Generate `nsig` significant decimal digits of a positive finite value into
-   `out` (ASCII, no terminator). Returns the base-10 exponent of the leading
-   digit, i.e. value ~= (out[0].out[1..]) * 10^E. Rounding is half-up and may
-   carry into a new leading digit, bumping the returned exponent. */
-static int _pf_gendigits(double v, int nsig, char *out) {
-    int E = (int)floor(log10(v));
-    double scale = v / pow(10.0, (double)E);
-    /* Correct estimate errors so scale lands in [1, 10). */
-    if (scale >= 10.0) { scale /= 10.0; E++; }
-    else if (scale < 1.0) { scale *= 10.0; E--; }
-
-    for (int i = 0; i < nsig; i++) {
-        int d = (int)scale;
-        if (d < 0) d = 0; else if (d > 9) d = 9;
-        out[i] = (char)('0' + d);
-        scale = (scale - d) * 10.0;
-    }
-
-    if (scale >= 5.0) {           /* round up based on the next digit */
-        int i = nsig - 1;
-        while (i >= 0) {
-            if (out[i] == '9') { out[i] = '0'; i--; }
-            else { out[i]++; break; }
-        }
-        if (i < 0) { out[0] = '1'; E++; }  /* all nines carried out */
-    }
-    return E;
-}
-
-/* Append the two-or-more-digit exponent field of %e/%g ("e+NN"). */
-static void _pf_put_exp(char *mbuf, int *mlen, int E, int upper) {
-    int m = *mlen;
-    mbuf[m++] = upper ? 'E' : 'e';
-    int ex = E; char es = '+';
-    if (ex < 0) { es = '-'; ex = -ex; }
-    mbuf[m++] = es;
-    char eb[8]; int el = 0;
-    if (ex == 0) eb[el++] = '0';
-    while (ex > 0) { eb[el++] = (char)('0' + ex % 10); ex /= 10; }
-    while (el < 2) eb[el++] = '0';
-    while (el > 0) mbuf[m++] = eb[--el];
-    *mlen = m;
-}
-
-/* Format a floating-point value for the %e/%f/%g conversions (and uppercase
-   variants), honoring precision, width, padding and sign flags. */
-static void _pf_putfloat(struct _pf_state *st, double v, char conv,
-                         int precision, int width, char pad,
-                         int left_align, int plus, int space, int alt) {
-    int upper = (conv >= 'A' && conv <= 'Z');
-    char lc = upper ? (char)(conv - 'A' + 'a') : conv;
-
-    _dbl_bits bits; bits.d = v;
-    int neg = (int)(bits.u >> 63);
-    uint64_t expo = (bits.u >> 52) & 0x7FF;
-    uint64_t mant = bits.u & 0x000FFFFFFFFFFFFFULL;
-
-    char sign = 0;
-    if (neg) sign = '-';
-    else if (plus) sign = '+';
-    else if (space) sign = ' ';
-
-    /* Infinity / NaN: never zero-padded. */
-    if (expo == 0x7FF) {
-        const char *word = mant ? (upper ? "NAN" : "nan") : (upper ? "INF" : "inf");
-        if (mant) sign = 0;
-        char tmp[8]; int tl = 0;
-        if (sign) tmp[tl++] = sign;
-        for (const char *p = word; *p; p++) tmp[tl++] = *p;
-        if (!left_align) for (int w = tl; w < width; w++) _pf_putc(st, ' ');
-        for (int i = 0; i < tl; i++) _pf_putc(st, tmp[i]);
-        if (left_align) for (int w = tl; w < width; w++) _pf_putc(st, ' ');
-        return;
-    }
-
-    if (precision < 0) precision = 6;
-    if (precision > 340) precision = 340;
-
-    double av = neg ? -v : v;
-
-    char mbuf[800];
-    int mlen = 0;
-
-    if (lc == 'e') {
-        int nsig = precision + 1;
-        char dig[400];
-        int E;
-        if (av == 0.0) { for (int i = 0; i < nsig; i++) dig[i] = '0'; E = 0; }
-        else E = _pf_gendigits(av, nsig, dig);
-        mbuf[mlen++] = dig[0];
-        if (precision > 0 || alt) {
-            mbuf[mlen++] = '.';
-            for (int i = 1; i <= precision; i++) mbuf[mlen++] = dig[i];
-        }
-        _pf_put_exp(mbuf, &mlen, E, upper);
-    }
-    else if (lc == 'f') {
-        if (av == 0.0) {
-            mbuf[mlen++] = '0';
-            if (precision > 0 || alt) {
-                mbuf[mlen++] = '.';
-                for (int i = 0; i < precision; i++) mbuf[mlen++] = '0';
-            }
-        } else {
-            int Ef = _pf_exp10(av);
-            int keep = Ef + 1 + precision;
-            if (keep <= 0) {
-                char d1[4];
-                _pf_gendigits(av, 1, d1);
-                int roundUp = (keep == 0 && d1[0] >= '5');
-                mbuf[mlen++] = '0';
-                if (precision > 0 || alt) {
-                    mbuf[mlen++] = '.';
-                    for (int i = 0; i < precision; i++) mbuf[mlen++] = '0';
-                }
-                if (roundUp) mbuf[mlen - 1] = '1';
-            } else {
-                if (keep > 380) keep = 380;
-                char dig[400];
-                int E = _pf_gendigits(av, keep, dig);
-                int len = keep;
-                int intlen = (E >= 0) ? (E + 1) : 0;
-                if (intlen == 0) mbuf[mlen++] = '0';
-                else for (int i = 0; i < intlen; i++) mbuf[mlen++] = (i < len ? dig[i] : '0');
-                if (precision > 0 || alt) {
-                    mbuf[mlen++] = '.';
-                    if (E < 0) {
-                        int lead = -E - 1;
-                        for (int k = 0; k < precision; k++) {
-                            if (k < lead) mbuf[mlen++] = '0';
-                            else { int idx = k - lead; mbuf[mlen++] = (idx < len ? dig[idx] : '0'); }
-                        }
-                    } else {
-                        for (int k = 0; k < precision; k++) {
-                            int idx = intlen + k;
-                            mbuf[mlen++] = (idx < len ? dig[idx] : '0');
-                        }
-                    }
-                }
-            }
-        }
-    }
-    else { /* 'g' / 'G' */
-        int P = precision; if (P == 0) P = 1;
-        char dig[400];
-        int E;
-        if (av == 0.0) { E = 0; for (int i = 0; i < P; i++) dig[i] = '0'; }
-        else E = _pf_gendigits(av, P, dig);
-        int len = P;
-        int useExp = (E < -4 || E >= P);
-        int hasDot = 0;
-        if (useExp) {
-            int fp = P - 1;
-            mbuf[mlen++] = dig[0];
-            if (fp > 0 || alt) {
-                mbuf[mlen++] = '.'; hasDot = 1;
-                for (int i = 1; i <= fp; i++) mbuf[mlen++] = dig[i];
-            }
-            if (!alt && hasDot) {
-                while (mbuf[mlen - 1] == '0') mlen--;
-                if (mbuf[mlen - 1] == '.') mlen--;
-            }
-            _pf_put_exp(mbuf, &mlen, E, upper);
-        } else {
-            int fp = P - 1 - E;
-            if (fp < 0) fp = 0;
-            int intlen = (E >= 0) ? (E + 1) : 0;
-            if (intlen == 0) mbuf[mlen++] = '0';
-            else for (int i = 0; i < intlen; i++) mbuf[mlen++] = (i < len ? dig[i] : '0');
-            if (fp > 0 || alt) {
-                mbuf[mlen++] = '.'; hasDot = 1;
-                if (E < 0) {
-                    int lead = -E - 1;
-                    for (int k = 0; k < fp; k++) {
-                        if (k < lead) mbuf[mlen++] = '0';
-                        else { int idx = k - lead; mbuf[mlen++] = (idx < len ? dig[idx] : '0'); }
-                    }
-                } else {
-                    for (int k = 0; k < fp; k++) {
-                        int idx = intlen + k;
-                        mbuf[mlen++] = (idx < len ? dig[idx] : '0');
-                    }
-                }
-            }
-            if (!alt && hasDot) {
-                while (mbuf[mlen - 1] == '0') mlen--;
-                if (mbuf[mlen - 1] == '.') mlen--;
-            }
-        }
-    }
-
-    int total = (sign ? 1 : 0) + mlen;
-    if (!left_align && pad == '0') {
-        if (sign) _pf_putc(st, sign);
-        for (int w = total; w < width; w++) _pf_putc(st, '0');
-        for (int i = 0; i < mlen; i++) _pf_putc(st, mbuf[i]);
-    } else if (!left_align) {
-        for (int w = total; w < width; w++) _pf_putc(st, ' ');
-        if (sign) _pf_putc(st, sign);
-        for (int i = 0; i < mlen; i++) _pf_putc(st, mbuf[i]);
-    } else {
-        if (sign) _pf_putc(st, sign);
-        for (int i = 0; i < mlen; i++) _pf_putc(st, mbuf[i]);
-        for (int w = total; w < width; w++) _pf_putc(st, ' ');
-    }
-}
-
 int vsnprintf(char *buf, size_t size, const char *fmt, va_list ap) {
     struct _pf_state st;
     st.buf = buf;
@@ -1579,9 +1363,18 @@ int vsnprintf(char *buf, size_t size, const char *fmt, va_list ap) {
         case 'f': case 'F':
         case 'e': case 'E':
         case 'g': case 'G': {
+            /* Consume the argument either way: skipping it would desync every
+               later conversion in the same format string. */
             double dv = va_arg(ap, double);
+            if (_pf_putfloat) {
                 _pf_putfloat(&st, dv, *fmt, precision, width, pad,
                              left_align, plus, space, alt);
+            } else {
+                /* printf_float.o was not linked in; echo the spec so the gap
+                   is visible rather than silently printing a wrong number. */
+                _pf_putc(&st, '%');
+                _pf_putc(&st, *fmt);
+            }
             break;
         }
         case '%':

programs/lib/libc/printf_float.c

@@ -0,0 +1,233 @@
+/*
+    * printf_float.c
+    * Floating-point conversions (%e/%f/%g and uppercase variants) for the
+    * printf family. Kept in its own translation unit -- and therefore its own
+    * archive member -- so that --gc-sections can drop it, along with the
+    * pow/exp/log it drags in, from the many programs that only ever format
+    * integers and strings. vsnprintf reaches this through a weak reference;
+    * see printf_internal.h and lib/libc/Makefile.
+    * Copyright (c) 2026 Daniel Hammer
+*/
+
+#include <stddef.h>
+#include <stdint.h>
+#include <math.h>
+
+#include "printf_internal.h"
+
+/* Base-10 exponent of the leading digit of a positive finite value, i.e. the
+   E such that value = m * 10^E with m in [1, 10). No rounding is applied. */
+static int _pf_exp10(double v) {
+    int E = (int)floor(log10(v));
+    double s = v / pow(10.0, (double)E);
+    if (s >= 10.0) E++;
+    else if (s < 1.0) E--;
+    return E;
+}
+
+/* Generate `nsig` significant decimal digits of a positive finite value into
+   `out` (ASCII, no terminator). Returns the base-10 exponent of the leading
+   digit, i.e. value ~= (out[0].out[1..]) * 10^E. Rounding is half-up and may
+   carry into a new leading digit, bumping the returned exponent. */
+static int _pf_gendigits(double v, int nsig, char *out) {
+    int E = (int)floor(log10(v));
+    double scale = v / pow(10.0, (double)E);
+    /* Correct estimate errors so scale lands in [1, 10). */
+    if (scale >= 10.0) { scale /= 10.0; E++; }
+    else if (scale < 1.0) { scale *= 10.0; E--; }
+
+    for (int i = 0; i < nsig; i++) {
+        int d = (int)scale;
+        if (d < 0) d = 0; else if (d > 9) d = 9;
+        out[i] = (char)('0' + d);
+        scale = (scale - d) * 10.0;
+    }
+
+    if (scale >= 5.0) {           /* round up based on the next digit */
+        int i = nsig - 1;
+        while (i >= 0) {
+            if (out[i] == '9') { out[i] = '0'; i--; }
+            else { out[i]++; break; }
+        }
+        if (i < 0) { out[0] = '1'; E++; }  /* all nines carried out */
+    }
+    return E;
+}
+
+/* Append the two-or-more-digit exponent field of %e/%g ("e+NN"). */
+static void _pf_put_exp(char *mbuf, int *mlen, int E, int upper) {
+    int m = *mlen;
+    mbuf[m++] = upper ? 'E' : 'e';
+    int ex = E; char es = '+';
+    if (ex < 0) { es = '-'; ex = -ex; }
+    mbuf[m++] = es;
+    char eb[8]; int el = 0;
+    if (ex == 0) eb[el++] = '0';
+    while (ex > 0) { eb[el++] = (char)('0' + ex % 10); ex /= 10; }
+    while (el < 2) eb[el++] = '0';
+    while (el > 0) mbuf[m++] = eb[--el];
+    *mlen = m;
+}
+
+/* Format a floating-point value for the %e/%f/%g conversions (and uppercase
+   variants), honoring precision, width, padding and sign flags. */
+void _pf_putfloat(struct _pf_state *st, double v, char conv,
+                  int precision, int width, char pad,
+                  int left_align, int plus, int space, int alt) {
+    int upper = (conv >= 'A' && conv <= 'Z');
+    char lc = upper ? (char)(conv - 'A' + 'a') : conv;
+
+    _dbl_bits bits; bits.d = v;
+    int neg = (int)(bits.u >> 63);
+    uint64_t expo = (bits.u >> 52) & 0x7FF;
+    uint64_t mant = bits.u & 0x000FFFFFFFFFFFFFULL;
+
+    char sign = 0;
+    if (neg) sign = '-';
+    else if (plus) sign = '+';
+    else if (space) sign = ' ';
+
+    /* Infinity / NaN: never zero-padded. */
+    if (expo == 0x7FF) {
+        const char *word = mant ? (upper ? "NAN" : "nan") : (upper ? "INF" : "inf");
+        if (mant) sign = 0;
+        char tmp[8]; int tl = 0;
+        if (sign) tmp[tl++] = sign;
+        for (const char *p = word; *p; p++) tmp[tl++] = *p;
+        if (!left_align) for (int w = tl; w < width; w++) _pf_putc(st, ' ');
+        for (int i = 0; i < tl; i++) _pf_putc(st, tmp[i]);
+        if (left_align) for (int w = tl; w < width; w++) _pf_putc(st, ' ');
+        return;
+    }
+
+    if (precision < 0) precision = 6;
+    if (precision > 340) precision = 340;
+
+    double av = neg ? -v : v;
+
+    char mbuf[800];
+    int mlen = 0;
+
+    if (lc == 'e') {
+        int nsig = precision + 1;
+        char dig[400];
+        int E;
+        if (av == 0.0) { for (int i = 0; i < nsig; i++) dig[i] = '0'; E = 0; }
+        else E = _pf_gendigits(av, nsig, dig);
+        mbuf[mlen++] = dig[0];
+        if (precision > 0 || alt) {
+            mbuf[mlen++] = '.';
+            for (int i = 1; i <= precision; i++) mbuf[mlen++] = dig[i];
+        }
+        _pf_put_exp(mbuf, &mlen, E, upper);
+    }
+    else if (lc == 'f') {
+        if (av == 0.0) {
+            mbuf[mlen++] = '0';
+            if (precision > 0 || alt) {
+                mbuf[mlen++] = '.';
+                for (int i = 0; i < precision; i++) mbuf[mlen++] = '0';
+            }
+        } else {
+            int Ef = _pf_exp10(av);
+            int keep = Ef + 1 + precision;
+            if (keep <= 0) {
+                char d1[4];
+                _pf_gendigits(av, 1, d1);
+                int roundUp = (keep == 0 && d1[0] >= '5');
+                mbuf[mlen++] = '0';
+                if (precision > 0 || alt) {
+                    mbuf[mlen++] = '.';
+                    for (int i = 0; i < precision; i++) mbuf[mlen++] = '0';
+                }
+                if (roundUp) mbuf[mlen - 1] = '1';
+            } else {
+                if (keep > 380) keep = 380;
+                char dig[400];
+                int E = _pf_gendigits(av, keep, dig);
+                int len = keep;
+                int intlen = (E >= 0) ? (E + 1) : 0;
+                if (intlen == 0) mbuf[mlen++] = '0';
+                else for (int i = 0; i < intlen; i++) mbuf[mlen++] = (i < len ? dig[i] : '0');
+                if (precision > 0 || alt) {
+                    mbuf[mlen++] = '.';
+                    if (E < 0) {
+                        int lead = -E - 1;
+                        for (int k = 0; k < precision; k++) {
+                            if (k < lead) mbuf[mlen++] = '0';
+                            else { int idx = k - lead; mbuf[mlen++] = (idx < len ? dig[idx] : '0'); }
+                        }
+                    } else {
+                        for (int k = 0; k < precision; k++) {
+                            int idx = intlen + k;
+                            mbuf[mlen++] = (idx < len ? dig[idx] : '0');
+                        }
+                    }
+                }
+            }
+        }
+    }
+    else { /* 'g' / 'G' */
+        int P = precision; if (P == 0) P = 1;
+        char dig[400];
+        int E;
+        if (av == 0.0) { E = 0; for (int i = 0; i < P; i++) dig[i] = '0'; }
+        else E = _pf_gendigits(av, P, dig);
+        int len = P;
+        int useExp = (E < -4 || E >= P);
+        int hasDot = 0;
+        if (useExp) {
+            int fp = P - 1;
+            mbuf[mlen++] = dig[0];
+            if (fp > 0 || alt) {
+                mbuf[mlen++] = '.'; hasDot = 1;
+                for (int i = 1; i <= fp; i++) mbuf[mlen++] = dig[i];
+            }
+            if (!alt && hasDot) {
+                while (mbuf[mlen - 1] == '0') mlen--;
+                if (mbuf[mlen - 1] == '.') mlen--;
+            }
+            _pf_put_exp(mbuf, &mlen, E, upper);
+        } else {
+            int fp = P - 1 - E;
+            if (fp < 0) fp = 0;
+            int intlen = (E >= 0) ? (E + 1) : 0;
+            if (intlen == 0) mbuf[mlen++] = '0';
+            else for (int i = 0; i < intlen; i++) mbuf[mlen++] = (i < len ? dig[i] : '0');
+            if (fp > 0 || alt) {
+                mbuf[mlen++] = '.'; hasDot = 1;
+                if (E < 0) {
+                    int lead = -E - 1;
+                    for (int k = 0; k < fp; k++) {
+                        if (k < lead) mbuf[mlen++] = '0';
+                        else { int idx = k - lead; mbuf[mlen++] = (idx < len ? dig[idx] : '0'); }
+                    }
+                } else {
+                    for (int k = 0; k < fp; k++) {
+                        int idx = intlen + k;
+                        mbuf[mlen++] = (idx < len ? dig[idx] : '0');
+                    }
+                }
+            }
+            if (!alt && hasDot) {
+                while (mbuf[mlen - 1] == '0') mlen--;
+                if (mbuf[mlen - 1] == '.') mlen--;
+            }
+        }
+    }
+
+    int total = (sign ? 1 : 0) + mlen;
+    if (!left_align && pad == '0') {
+        if (sign) _pf_putc(st, sign);
+        for (int w = total; w < width; w++) _pf_putc(st, '0');
+        for (int i = 0; i < mlen; i++) _pf_putc(st, mbuf[i]);
+    } else if (!left_align) {
+        for (int w = total; w < width; w++) _pf_putc(st, ' ');
+        if (sign) _pf_putc(st, sign);
+        for (int i = 0; i < mlen; i++) _pf_putc(st, mbuf[i]);
+    } else {
+        if (sign) _pf_putc(st, sign);
+        for (int i = 0; i < mlen; i++) _pf_putc(st, mbuf[i]);
+        for (int w = total; w < width; w++) _pf_putc(st, ' ');
+    }
+}

programs/lib/libc/printf_internal.h

@@ -0,0 +1,39 @@
+/*
+    * printf_internal.h
+    * Shared state between the integer printf core (libc.c) and the optional
+    * floating-point conversion module (printf_float.c).
+    * Copyright (c) 2026 Daniel Hammer
+*/
+
+#ifndef _LIBC_PRINTF_INTERNAL_H
+#define _LIBC_PRINTF_INTERNAL_H
+
+#include <stddef.h>
+#include <stdint.h>
+
+/* Output cursor shared by every conversion. `pos` counts the characters a
+   conversion WOULD have written, so it may run past `max`; only writes below
+   `max` land in `buf`. That is what gives snprintf its C99 return value. */
+struct _pf_state {
+    char  *buf;
+    size_t pos;
+    size_t max;
+};
+
+/* Defined in libc.c. External rather than static so the float module can
+   reach it; it is the only core helper the float conversions need. */
+void _pf_putc(struct _pf_state *st, char c);
+
+/* Union for double bit manipulation (used by float formatting and math). */
+typedef union { double d; uint64_t u; } _dbl_bits;
+
+/* Defined in printf_float.c, which is a SEPARATE archive member so that
+   --gc-sections can drop the decimal-conversion and pow/exp/log code from
+   programs that never format a float. vsnprintf calls this through a WEAK
+   reference: link with -Wl,-u,_pf_putfloat to pull the module in. Without
+   that flag %e/%f/%g echo their conversion spec instead of a number. */
+void _pf_putfloat(struct _pf_state *st, double v, char conv,
+                  int precision, int width, char pad,
+                  int left_align, int plus, int space, int alt);
+
+#endif /* _LIBC_PRINTF_INTERNAL_H */

programs/src/audio/Makefile

@@ -62,7 +62,7 @@ TARGET := $(BINDIR)/apps/audio/audio.elf
 
 all: $(TARGET)
 
-$(TARGET): $(OBJS) $(LINK_LD) Makefile
+$(TARGET): $(OBJS) $(LINK_LD) Makefile $(LIBDIR)/libc/liblibc.a
 	mkdir -p $(BINDIR)/apps/audio
 	$(CXX) $(CXXFLAGS) $(LDFLAGS) $(OBJS) $(LIBDIR)/libc/liblibc.a -o $@
 

programs/src/bluetooth/Makefile

@@ -62,7 +62,7 @@ TARGET := $(BINDIR)/apps/bluetooth/bluetooth.elf
 
 all: $(TARGET)
 
-$(TARGET): $(OBJS) $(LINK_LD) Makefile
+$(TARGET): $(OBJS) $(LINK_LD) Makefile $(LIBDIR)/libc/liblibc.a
 	mkdir -p $(BINDIR)/apps/bluetooth
 	$(CXX) $(CXXFLAGS) $(LDFLAGS) $(OBJS) $(LIBDIR)/libc/liblibc.a -o $@
 

programs/src/calculator/Makefile

@@ -62,7 +62,7 @@ TARGET := $(BINDIR)/apps/calculator/calculator.elf
 
 all: $(TARGET)
 
-$(TARGET): $(OBJS) $(LINK_LD) Makefile
+$(TARGET): $(OBJS) $(LINK_LD) Makefile $(LIBDIR)/libc/liblibc.a
 	mkdir -p $(BINDIR)/apps/calculator
 	$(CXX) $(CXXFLAGS) $(LDFLAGS) $(OBJS) $(LIBDIR)/libc/liblibc.a -o $@
 

programs/src/charmap/Makefile

@@ -62,7 +62,7 @@ TARGET := $(BINDIR)/apps/charmap/charmap.elf
 
 all: $(TARGET)
 
-$(TARGET): $(OBJS) $(LINK_LD) Makefile
+$(TARGET): $(OBJS) $(LINK_LD) Makefile $(LIBDIR)/libc/liblibc.a
 	mkdir -p $(BINDIR)/apps/charmap
 	$(CXX) $(CXXFLAGS) $(LDFLAGS) $(OBJS) $(LIBDIR)/libc/liblibc.a -o $@
 

programs/src/devexplorer/Makefile

@@ -63,7 +63,7 @@ TARGET := $(BINDIR)/apps/devexplorer/devexplorer.elf
 
 all: $(TARGET)
 
-$(TARGET): $(OBJS) $(LINK_LD) Makefile
+$(TARGET): $(OBJS) $(LINK_LD) Makefile $(LIBDIR)/libc/liblibc.a
 	mkdir -p $(BINDIR)/apps/devexplorer
 	$(CXX) $(CXXFLAGS) $(LDFLAGS) $(OBJS) $(LIBDIR)/libc/liblibc.a -o $@
 

programs/src/dhcp/main.cpp

@@ -7,96 +7,11 @@
 
 #include <montauk/syscall.h>
 #include <montauk/string.h>
+#include <libc/stdio.h>
 
 using montauk::memcpy;
 using montauk::memset;
 
-// ---- Minimal snprintf (no libc available) ----
-
-using va_list = __builtin_va_list;
-#define va_start __builtin_va_start
-#define va_end   __builtin_va_end
-#define va_arg   __builtin_va_arg
-
-struct PfState {
-    char*  buf;
-    int    pos;
-    int    max;
-};
-
-static void pf_putc(PfState* st, char c) {
-    if (st->pos < st->max) st->buf[st->pos] = c;
-    st->pos++;
-}
-
-static void pf_putnum(PfState* st, unsigned long val, int base, int width, char pad, int neg) {
-    char tmp[24];
-    int i = 0;
-    const char* digits = "0123456789abcdef";
-    if (val == 0) { tmp[i++] = '0'; }
-    else { while (val > 0) { tmp[i++] = digits[val % base]; val /= base; } }
-    int total = (neg ? 1 : 0) + i;
-    if (neg && pad == '0') pf_putc(st, '-');
-    for (int w = total; w < width; w++) pf_putc(st, pad);
-    if (neg && pad != '0') pf_putc(st, '-');
-    while (i > 0) pf_putc(st, tmp[--i]);
-}
-
-static int vsnprintf(char* buf, int size, const char* fmt, va_list ap) {
-    PfState st;
-    st.buf = buf;
-    st.pos = 0;
-    st.max = size > 0 ? size - 1 : 0;
-    while (*fmt) {
-        if (*fmt != '%') { pf_putc(&st, *fmt++); continue; }
-        fmt++;
-        char pad = ' ';
-        if (*fmt == '0') { pad = '0'; fmt++; }
-        int width = 0;
-        while (*fmt >= '0' && *fmt <= '9') { width = width * 10 + (*fmt - '0'); fmt++; }
-        if (*fmt == 'l') fmt++;
-        switch (*fmt) {
-        case 'd': case 'i': {
-            long val = va_arg(ap, int);
-            int neg = 0; unsigned long uval;
-            if (val < 0) { neg = 1; uval = (unsigned long)(-val); }
-            else uval = (unsigned long)val;
-            pf_putnum(&st, uval, 10, width, pad, neg);
-            break;
-        }
-        case 'u': { unsigned val = va_arg(ap, unsigned); pf_putnum(&st, val, 10, width, pad, 0); break; }
-        case 'x': { unsigned val = va_arg(ap, unsigned); pf_putnum(&st, val, 16, width, pad, 0); break; }
-        case 's': {
-            const char* s = va_arg(ap, const char*);
-            if (!s) s = "(null)";
-            int slen = 0; while (s[slen]) slen++;
-            for (int w = slen; w < width; w++) pf_putc(&st, ' ');
-            for (int j = 0; j < slen; j++) pf_putc(&st, s[j]);
-            break;
-        }
-        case 'c': { char c = (char)va_arg(ap, int); pf_putc(&st, c); break; }
-        case '%': pf_putc(&st, '%'); break;
-        default: pf_putc(&st, '%'); pf_putc(&st, *fmt); break;
-        }
-        if (*fmt) fmt++;
-    }
-    if (size > 0) {
-        if (st.pos < size) st.buf[st.pos] = '\0';
-        else st.buf[size - 1] = '\0';
-    }
-    return st.pos;
-}
-
-static int snprintf(char* buf, int size, const char* fmt, ...) {
-    va_list ap;
-    va_start(ap, fmt);
-    int ret = vsnprintf(buf, size, fmt, ap);
-    va_end(ap);
-    return ret;
-}
-
-
-
 // ---- DHCP constants ----
 
 static constexpr uint8_t  BOOTREQUEST = 1;

programs/src/disks/Makefile

@@ -62,7 +62,7 @@ TARGET := $(BINDIR)/apps/disks/disks.elf
 
 all: $(TARGET)
 
-$(TARGET): $(OBJS) $(LINK_LD) Makefile
+$(TARGET): $(OBJS) $(LINK_LD) Makefile $(LIBDIR)/libc/liblibc.a
 	mkdir -p $(BINDIR)/apps/disks
 	$(CXX) $(CXXFLAGS) $(LDFLAGS) $(OBJS) $(LIBDIR)/libc/liblibc.a -o $@
 

programs/src/doom/Makefile

@@ -185,7 +185,7 @@ TARGET := $(BINDIR)/apps/doom/doom.elf
 
 all: $(TARGET)
 
-$(TARGET): $(ALL_OBJS) $(LINK_LD) Makefile
+$(TARGET): $(ALL_OBJS) $(LINK_LD) Makefile $(LOADER_LIB)/liblibloader.a $(LIBDIR)/libc/liblibc.a
 	mkdir -p $(BINDIR)/apps/doom
 	$(LD) $(CFLAGS) $(LDFLAGS) $(ALL_OBJS) $(LOADER_LIB)/liblibloader.a $(LIBDIR)/libc/liblibc.a -o $@
 

programs/src/httpd/main.cpp

@@ -8,96 +8,13 @@
 
 #include <montauk/syscall.h>
 #include <montauk/string.h>
+#include <libc/stdio.h>
 
 using montauk::slen;
 using montauk::streq;
 using montauk::starts_with;
 using montauk::skip_spaces;
 
-// ---- Minimal snprintf (no libc available) ----
-
-using va_list = __builtin_va_list;
-#define va_start __builtin_va_start
-#define va_end   __builtin_va_end
-#define va_arg   __builtin_va_arg
-
-struct PfState {
-    char*  buf;
-    int    pos;
-    int    max;
-};
-
-static void pf_putc(PfState* st, char c) {
-    if (st->pos < st->max) st->buf[st->pos] = c;
-    st->pos++;
-}
-
-static void pf_putnum(PfState* st, unsigned long val, int base, int width, char pad, int neg) {
-    char tmp[24];
-    int i = 0;
-    const char* digits = "0123456789abcdef";
-    if (val == 0) { tmp[i++] = '0'; }
-    else { while (val > 0) { tmp[i++] = digits[val % base]; val /= base; } }
-    int total = (neg ? 1 : 0) + i;
-    if (neg && pad == '0') pf_putc(st, '-');
-    for (int w = total; w < width; w++) pf_putc(st, pad);
-    if (neg && pad != '0') pf_putc(st, '-');
-    while (i > 0) pf_putc(st, tmp[--i]);
-}
-
-static int vsnprintf(char* buf, int size, const char* fmt, va_list ap) {
-    PfState st;
-    st.buf = buf;
-    st.pos = 0;
-    st.max = size > 0 ? size - 1 : 0;
-    while (*fmt) {
-        if (*fmt != '%') { pf_putc(&st, *fmt++); continue; }
-        fmt++;
-        char pad = ' ';
-        if (*fmt == '0') { pad = '0'; fmt++; }
-        int width = 0;
-        while (*fmt >= '0' && *fmt <= '9') { width = width * 10 + (*fmt - '0'); fmt++; }
-        if (*fmt == 'l') fmt++;
-        switch (*fmt) {
-        case 'd': case 'i': {
-            long val = va_arg(ap, int);
-            int neg = 0; unsigned long uval;
-            if (val < 0) { neg = 1; uval = (unsigned long)(-val); }
-            else uval = (unsigned long)val;
-            pf_putnum(&st, uval, 10, width, pad, neg);
-            break;
-        }
-        case 'u': { unsigned val = va_arg(ap, unsigned); pf_putnum(&st, val, 10, width, pad, 0); break; }
-        case 'x': { unsigned val = va_arg(ap, unsigned); pf_putnum(&st, val, 16, width, pad, 0); break; }
-        case 's': {
-            const char* s = va_arg(ap, const char*);
-            if (!s) s = "(null)";
-            int slen = 0; while (s[slen]) slen++;
-            for (int w = slen; w < width; w++) pf_putc(&st, ' ');
-            for (int j = 0; j < slen; j++) pf_putc(&st, s[j]);
-            break;
-        }
-        case 'c': { char c = (char)va_arg(ap, int); pf_putc(&st, c); break; }
-        case '%': pf_putc(&st, '%'); break;
-        default: pf_putc(&st, '%'); pf_putc(&st, *fmt); break;
-        }
-        if (*fmt) fmt++;
-    }
-    if (size > 0) {
-        if (st.pos < size) st.buf[st.pos] = '\0';
-        else st.buf[size - 1] = '\0';
-    }
-    return st.pos;
-}
-
-static int snprintf(char* buf, int size, const char* fmt, ...) {
-    va_list ap;
-    va_start(ap, fmt);
-    int ret = vsnprintf(buf, size, fmt, ap);
-    va_end(ap);
-    return ret;
-}
-
 // ---- IP/port parsing ----
 
 static bool parse_uint16(const char* s, uint16_t* out) {

programs/src/init/main.cpp

@@ -6,74 +6,7 @@
 */
 
 #include <montauk/syscall.h>
-
+#include <libc/stdio.h>
-// ---- Minimal snprintf ----
-
-using va_list = __builtin_va_list;
-#define va_start __builtin_va_start
-#define va_end   __builtin_va_end
-#define va_arg   __builtin_va_arg
-
-struct PfState { char* buf; int pos; int max; };
-
-static void pf_putc(PfState* st, char c) {
-    if (st->pos < st->max) st->buf[st->pos] = c;
-    st->pos++;
-}
-
-static void pf_putnum(PfState* st, unsigned long val, int base, int width, char pad, int neg) {
-    char tmp[24]; int i = 0;
-    const char* digits = "0123456789abcdef";
-    if (val == 0) { tmp[i++] = '0'; }
-    else { while (val > 0) { tmp[i++] = digits[val % base]; val /= base; } }
-    int total = (neg ? 1 : 0) + i;
-    if (neg && pad == '0') pf_putc(st, '-');
-    for (int w = total; w < width; w++) pf_putc(st, pad);
-    if (neg && pad != '0') pf_putc(st, '-');
-    while (i > 0) pf_putc(st, tmp[--i]);
-}
-
-static int vsnprintf(char* buf, int size, const char* fmt, va_list ap) {
-    PfState st; st.buf = buf; st.pos = 0; st.max = size > 0 ? size - 1 : 0;
-    while (*fmt) {
-        if (*fmt != '%') { pf_putc(&st, *fmt++); continue; }
-        fmt++;
-        char pad = ' ';
-        if (*fmt == '0') { pad = '0'; fmt++; }
-        int width = 0;
-        while (*fmt >= '0' && *fmt <= '9') { width = width * 10 + (*fmt - '0'); fmt++; }
-        if (*fmt == 'l') fmt++;
-        switch (*fmt) {
-        case 'd': case 'i': {
-            long val = va_arg(ap, int);
-            int neg = 0; unsigned long uval;
-            if (val < 0) { neg = 1; uval = (unsigned long)(-val); } else uval = (unsigned long)val;
-            pf_putnum(&st, uval, 10, width, pad, neg); break;
-        }
-        case 'u': { unsigned val = va_arg(ap, unsigned); pf_putnum(&st, val, 10, width, pad, 0); break; }
-        case 'x': { unsigned val = va_arg(ap, unsigned); pf_putnum(&st, val, 16, width, pad, 0); break; }
-        case 's': {
-            const char* s = va_arg(ap, const char*); if (!s) s = "(null)";
-            int slen = 0; while (s[slen]) slen++;
-            for (int w = slen; w < width; w++) pf_putc(&st, ' ');
-            for (int j = 0; j < slen; j++) pf_putc(&st, s[j]);
-            break;
-        }
-        case 'c': { char c = (char)va_arg(ap, int); pf_putc(&st, c); break; }
-        case '%': pf_putc(&st, '%'); break;
-        default: pf_putc(&st, '%'); pf_putc(&st, *fmt); break;
-        }
-        if (*fmt) fmt++;
-    }
-    if (size > 0) { if (st.pos < size) st.buf[st.pos] = '\0'; else st.buf[size - 1] = '\0'; }
-    return st.pos;
-}
-
-static int snprintf(char* buf, int size, const char* fmt, ...) {
-    va_list ap; va_start(ap, fmt);
-    int ret = vsnprintf(buf, size, fmt, ap);
-    va_end(ap); return ret;
-}
 
 // ---- ANSI color codes ----
 

programs/src/installer/Makefile

@@ -63,7 +63,7 @@ TARGET := $(BINDIR)/apps/installer/installer.elf
 
 all: $(TARGET)
 
-$(TARGET): $(OBJS) $(LINK_LD) Makefile
+$(TARGET): $(OBJS) $(LINK_LD) Makefile $(LIBDIR)/libc/liblibc.a
 	mkdir -p $(BINDIR)/apps/installer
 	$(CXX) $(CXXFLAGS) $(LDFLAGS) $(OBJS) $(LIBDIR)/libc/liblibc.a -o $@
 

programs/src/irc/main.cpp

@@ -7,6 +7,7 @@
 
 #include <montauk/syscall.h>
 #include <montauk/string.h>
+#include <libc/stdio.h>
 
 using montauk::slen;
 using montauk::streq;
@@ -17,90 +18,6 @@ using montauk::strncpy;
 using montauk::memcpy;
 using montauk::memmove;
 
-// ---- Minimal snprintf (no libc available) ----
-
-using va_list = __builtin_va_list;
-#define va_start __builtin_va_start
-#define va_end   __builtin_va_end
-#define va_arg   __builtin_va_arg
-
-struct PfState {
-    char*  buf;
-    int    pos;
-    int    max;
-};
-
-static void pf_putc(PfState* st, char c) {
-    if (st->pos < st->max) st->buf[st->pos] = c;
-    st->pos++;
-}
-
-static void pf_putnum(PfState* st, unsigned long val, int base, int width, char pad, int neg) {
-    char tmp[24];
-    int i = 0;
-    const char* digits = "0123456789abcdef";
-    if (val == 0) { tmp[i++] = '0'; }
-    else { while (val > 0) { tmp[i++] = digits[val % base]; val /= base; } }
-    int total = (neg ? 1 : 0) + i;
-    if (neg && pad == '0') pf_putc(st, '-');
-    for (int w = total; w < width; w++) pf_putc(st, pad);
-    if (neg && pad != '0') pf_putc(st, '-');
-    while (i > 0) pf_putc(st, tmp[--i]);
-}
-
-static int vsnprintf(char* buf, int size, const char* fmt, va_list ap) {
-    PfState st;
-    st.buf = buf;
-    st.pos = 0;
-    st.max = size > 0 ? size - 1 : 0;
-    while (*fmt) {
-        if (*fmt != '%') { pf_putc(&st, *fmt++); continue; }
-        fmt++;
-        char pad = ' ';
-        if (*fmt == '0') { pad = '0'; fmt++; }
-        int width = 0;
-        while (*fmt >= '0' && *fmt <= '9') { width = width * 10 + (*fmt - '0'); fmt++; }
-        if (*fmt == 'l') fmt++;
-        switch (*fmt) {
-        case 'd': case 'i': {
-            long val = va_arg(ap, int);
-            int neg = 0; unsigned long uval;
-            if (val < 0) { neg = 1; uval = (unsigned long)(-val); }
-            else uval = (unsigned long)val;
-            pf_putnum(&st, uval, 10, width, pad, neg);
-            break;
-        }
-        case 'u': { unsigned val = va_arg(ap, unsigned); pf_putnum(&st, val, 10, width, pad, 0); break; }
-        case 'x': { unsigned val = va_arg(ap, unsigned); pf_putnum(&st, val, 16, width, pad, 0); break; }
-        case 's': {
-            const char* s = va_arg(ap, const char*);
-            if (!s) s = "(null)";
-            int slen = 0; while (s[slen]) slen++;
-            for (int w = slen; w < width; w++) pf_putc(&st, ' ');
-            for (int j = 0; j < slen; j++) pf_putc(&st, s[j]);
-            break;
-        }
-        case 'c': { char c = (char)va_arg(ap, int); pf_putc(&st, c); break; }
-        case '%': pf_putc(&st, '%'); break;
-        default: pf_putc(&st, '%'); pf_putc(&st, *fmt); break;
-        }
-        if (*fmt) fmt++;
-    }
-    if (size > 0) {
-        if (st.pos < size) st.buf[st.pos] = '\0';
-        else st.buf[size - 1] = '\0';
-    }
-    return st.pos;
-}
-
-static int snprintf(char* buf, int size, const char* fmt, ...) {
-    va_list ap;
-    va_start(ap, fmt);
-    int ret = vsnprintf(buf, size, fmt, ap);
-    va_end(ap);
-    return ret;
-}
-
 // Case-insensitive comparison for IRC commands
 static bool streqi(const char* a, const char* b) {
     while (*a && *b) {

programs/src/klog/Makefile

@@ -51,7 +51,7 @@ TARGET := $(BINDIR)/apps/klog/klog.elf
 
 all: $(TARGET)
 
-$(TARGET): $(OBJS) $(LINK_LD) Makefile
+$(TARGET): $(OBJS) $(LINK_LD) Makefile $(LIBDIR)/libc/liblibc.a
 	mkdir -p $(BINDIR)/apps/klog
 	$(CXX) $(CXXFLAGS) $(LDFLAGS) $(OBJS) $(LIBDIR)/libc/liblibc.a -o $@
 

programs/src/lua/Makefile

@@ -39,9 +39,13 @@ CFLAGS := \
     -isystem ../../include/libc \
     -isystem $(shell $(CC) -print-file-name=include)
 
+# -u _pf_putfloat forces liblibc.a's optional printf_float.o member to be
+# linked: Lua formats floats (%.14g in lobject.c, %f/%e/%g via string.format),
+# and vsnprintf only references the float conversions weakly.
 LDFLAGS := \
     -nostdlib \
     -Wl,--gc-sections \
+    -Wl,-u,_pf_putfloat \
     -T ../../link.ld
 
 CORE_SRCS := \

programs/src/mandelbrot/Makefile

@@ -62,7 +62,7 @@ TARGET := $(BINDIR)/apps/mandelbrot/mandelbrot.elf
 
 all: $(TARGET)
 
-$(TARGET): $(OBJS) $(LINK_LD) Makefile
+$(TARGET): $(OBJS) $(LINK_LD) Makefile $(LIBDIR)/libc/liblibc.a
 	mkdir -p $(BINDIR)/apps/mandelbrot
 	$(CXX) $(CXXFLAGS) $(LDFLAGS) $(OBJS) $(LIBDIR)/libc/liblibc.a -o $@
 

programs/src/music/Makefile

@@ -63,7 +63,7 @@ TARGET := $(BINDIR)/apps/music/music.elf
 
 all: $(TARGET)
 
-$(TARGET): $(OBJS) $(LINK_LD) Makefile
+$(TARGET): $(OBJS) $(LINK_LD) Makefile $(LIBDIR)/libc/liblibc.a
 	mkdir -p $(BINDIR)/apps/music
 	$(CXX) $(CXXFLAGS) $(LDFLAGS) $(OBJS) $(LIBDIR)/libc/liblibc.a -o $@
 

programs/src/paint/Makefile

@@ -62,7 +62,7 @@ TARGET := $(BINDIR)/apps/paint/paint.elf
 
 all: $(TARGET)
 
-$(TARGET): $(OBJS) $(LINK_LD) Makefile
+$(TARGET): $(OBJS) $(LINK_LD) Makefile $(LIBDIR)/libc/liblibc.a
 	mkdir -p $(BINDIR)/apps/paint
 	$(CXX) $(CXXFLAGS) $(LDFLAGS) $(OBJS) $(LIBDIR)/libc/liblibc.a -o $@
 

programs/src/pdfviewer/Makefile

@@ -63,7 +63,7 @@ LOADER_LIB := $(LIBDIR)/libloader/liblibloader.a
 
 all: $(TARGET)
 
-$(TARGET): $(OBJS) $(LINK_LD) Makefile $(LOADER_LIB)
+$(TARGET): $(OBJS) $(LINK_LD) Makefile $(LOADER_LIB) $(LIBDIR)/libc/liblibc.a
 	mkdir -p $(BINDIR)/apps/pdfviewer
 	$(CXX) $(CXXFLAGS) $(LDFLAGS) $(OBJS) $(LOADER_LIB) $(LIBDIR)/libc/liblibc.a -o $@
 

programs/src/powermgr/Makefile

@@ -51,7 +51,7 @@ TARGET := $(BINDIR)/apps/powermgr/powermgr.elf
 
 all: $(TARGET)
 
-$(TARGET): $(OBJS) $(LINK_LD) Makefile
+$(TARGET): $(OBJS) $(LINK_LD) Makefile $(LIBDIR)/libc/liblibc.a
 	mkdir -p $(BINDIR)/apps/powermgr
 	$(CXX) $(CXXFLAGS) $(LDFLAGS) $(OBJS) $(LIBDIR)/libc/liblibc.a -o $@
 

programs/src/printctl/Makefile

@@ -51,7 +51,7 @@ DEPS := $(OBJDIR)/main.d
 
 all: $(TARGET)
 
-$(TARGET): $(OBJDIR)/main.o $(LINK_LD) Makefile
+$(TARGET): $(OBJDIR)/main.o $(LINK_LD) Makefile $(LIBC_LIB)/liblibc.a
 	mkdir -p $(BINDIR)/os
 	$(CXX) $(CXXFLAGS) $(LDFLAGS) $(OBJDIR)/main.o $(TLS_LIB)/libtls.a $(BEARSSL)/libbearssl.a $(LIBC_LIB)/liblibc.a -o $@
 

programs/src/procmgr/Makefile

@@ -51,7 +51,7 @@ TARGET := $(BINDIR)/apps/procmgr/procmgr.elf
 
 all: $(TARGET)
 
-$(TARGET): $(OBJS) $(LINK_LD) Makefile
+$(TARGET): $(OBJS) $(LINK_LD) Makefile $(LIBDIR)/libc/liblibc.a
 	mkdir -p $(BINDIR)/apps/procmgr
 	$(CXX) $(CXXFLAGS) $(LDFLAGS) $(OBJS) $(LIBDIR)/libc/liblibc.a -o $@
 

programs/src/rpgdemo/Makefile

@@ -69,7 +69,7 @@ APP_DIR := $(BINDIR)/apps/rpgdemo
 
 all: $(TARGET) assets
 
-$(TARGET): $(OBJS) $(LINK_LD) Makefile
+$(TARGET): $(OBJS) $(LINK_LD) Makefile $(LIBDIR)/libc/liblibc.a
 	mkdir -p $(APP_DIR)
 	$(CXX) $(CXXFLAGS) $(LDFLAGS) $(OBJS) $(LIBDIR)/libc/liblibc.a -o $@
 

programs/src/spreadsheet/Makefile

@@ -63,7 +63,7 @@ LOADER_LIB := $(LIBDIR)/libloader/liblibloader.a
 
 all: $(TARGET)
 
-$(TARGET): $(OBJS) $(LINK_LD) Makefile $(LOADER_LIB)
+$(TARGET): $(OBJS) $(LINK_LD) Makefile $(LOADER_LIB) $(LIBDIR)/libc/liblibc.a
 	mkdir -p $(BINDIR)/apps/spreadsheet
 	$(CXX) $(CXXFLAGS) $(LDFLAGS) $(OBJS) $(LOADER_LIB) $(LIBDIR)/libc/liblibc.a -o $@
 

programs/src/tcc/Makefile

@@ -53,9 +53,13 @@ CFLAGS := \
     -isystem $(PROG_INC)/libc \
     -isystem $(shell $(CC) -print-file-name=include)
 
+# -u _pf_putfloat forces liblibc.a's optional printf_float.o member to be
+# linked: tcc formats floats when dumping constants (tccpp.c), and vsnprintf
+# only references the float conversions weakly.
 LDFLAGS := \
     -nostdlib \
     -Wl,--gc-sections \
+    -Wl,-u,_pf_putfloat \
     -T ../../link.ld
 
 # ---- Sources ----
@@ -110,7 +114,7 @@ $(OBJDIR)/%.o: %.S Makefile
 	@mkdir -p $(OBJDIR)
 	$(CC) $(CFLAGS) -MMD -MP -c $< -o $@
 
-$(SHARED_CRT_DIR)/liblibc.a $(SHARED_CRT_DIR)/crt1.o $(SHARED_CRT_DIR)/crti.o $(SHARED_CRT_DIR)/crtn.o:
+$(SHARED_CRT_DIR)/liblibc.a $(SHARED_CRT_DIR)/liblibc-full.a $(SHARED_CRT_DIR)/crt1.o $(SHARED_CRT_DIR)/crti.o $(SHARED_CRT_DIR)/crtn.o:
 	$(MAKE) -C $(SHARED_CRT_DIR)
 
 $(CRT_DIR)/crt1.o: $(SHARED_CRT_DIR)/crt1.o
@@ -125,7 +129,10 @@ $(CRT_DIR)/crtn.o: $(SHARED_CRT_DIR)/crtn.o
 	@mkdir -p $(CRT_DIR)
 	cp $< $@
 
-$(CRT_DIR)/libc.a: $(LIBDIR)/libc/liblibc.a
+# liblibc-full.a, not liblibc.a: programs compiled on-OS with tcc cannot pass
+# -u _pf_putfloat, so this sysroot ships the variant with the printf float path
+# already bound in. See lib/libc/Makefile.
+$(CRT_DIR)/libc.a: $(LIBDIR)/libc/liblibc-full.a
 	@mkdir -p $(CRT_DIR)
 	cp $< $@
 

programs/src/terminal/Makefile

@@ -51,7 +51,7 @@ TARGET := $(BINDIR)/apps/terminal/terminal.elf
 
 all: $(TARGET)
 
-$(TARGET): $(OBJS) $(LINK_LD) Makefile
+$(TARGET): $(OBJS) $(LINK_LD) Makefile $(LIBDIR)/libc/liblibc.a
 	mkdir -p $(BINDIR)/apps/terminal
 	$(CXX) $(CXXFLAGS) $(LDFLAGS) $(OBJS) $(LIBDIR)/libc/liblibc.a -o $@
 

programs/src/texteditor/Makefile

@@ -63,7 +63,7 @@ LOADER_LIB := $(LIBDIR)/libloader/liblibloader.a
 
 all: $(TARGET)
 
-$(TARGET): $(OBJS) $(LINK_LD) Makefile $(LOADER_LIB)
+$(TARGET): $(OBJS) $(LINK_LD) Makefile $(LOADER_LIB) $(LIBDIR)/libc/liblibc.a
 	mkdir -p $(BINDIR)/apps/texteditor
 	$(CXX) $(CXXFLAGS) $(LDFLAGS) $(OBJS) $(LOADER_LIB) $(LIBDIR)/libc/liblibc.a -o $@
 

programs/src/video/Makefile

@@ -51,7 +51,7 @@ TARGET := $(BINDIR)/apps/video/video.elf
 
 all: $(TARGET)
 
-$(TARGET): $(OBJS) $(LINK_LD) Makefile
+$(TARGET): $(OBJS) $(LINK_LD) Makefile $(LIBDIR)/libc/liblibc.a
 	mkdir -p $(BINDIR)/apps/video
 	$(CXX) $(CXXFLAGS) $(LDFLAGS) $(OBJS) $(LIBDIR)/libc/liblibc.a -o $@