feat: native GCC - cc1, cc1plus and the gcc driver run on MontaukOS

Cross-build GCC 14.2.0 with --host=x86_64-montauk: the driver, cc1,
cc1plus and collect2 now link as static Montauk ET_EXEC binaries
against the hosted libstdc++, and ship in the SDK. Together with the
native binutils, TCC and the target sysroot, MontaukOS carries a
complete self-contained C and C++ toolchain at 0:/sdk.

libc: anonymous mmap/munmap over SYS_ALLOC (GCC's page allocator
wants mmap; SYS_ALLOC memory is page-aligned by construction),
getpagesize, minimal sysconf, MB_CUR_MAX, isascii/toascii, POSIX id
typedefs (ino_t, dev_t, nlink_t, ...), struct stat fields switched to
proper POSIX types (st_size is a signed off_t now), and a
conventional _STDIO_H guard marker so GMP's FILE detection works.

Build recipe and the five host-build gotchas (bundled config.subs,
gettext removal, stdio guard sniffing, endianness cache preset,
sysroot sdk symlink) are documented in toolchain/README.md. The
devkit stages the driver as gcc.elf/g++.elf/cpp.elf, the backends in
the libexec layout the driver expects, a copy of ld where collect2
searches, and a 0:/tmp scratch dir. Ramdisk: 1604 files, 368 MB.

Co-Authored-By: Claude Fable 5 <[email protected]>

.gitignore

@@ -20,3 +20,4 @@ programs/lib/bearssl
 ramdisk.tar
 PLANS/.mcp.json
 toolchain/native/
+toolchain/native-gcc/

kernel/src/Api/BuildNo.hpp

@@ -12,4 +12,4 @@
 
 #pragma once
 
-#define MONTAUK_BUILD_NUMBER 18
+#define MONTAUK_BUILD_NUMBER 19

programs/GNUmakefile

@@ -405,6 +405,26 @@ ifneq ($(wildcard $(NATIVE_BIN)/as),)
 	cp -r ../toolchain/local/x86_64-montauk/include/c++ $(BINDIR)/sdk/include/c++
 	../toolchain/local/bin/x86_64-montauk-gcc -O2 ../toolchain/files/tls-test.c -o $(BINDIR)/sdk/bin/tls-test.elf
 	../toolchain/local/bin/x86_64-montauk-g++ -O2 ../toolchain/files/cxx-test.cpp -o $(BINDIR)/sdk/bin/cxx-test.elf
+ifneq ($(wildcard ../toolchain/native-gcc/sdk/bin/gcc),)
+	cp ../toolchain/native-gcc/sdk/bin/gcc $(BINDIR)/sdk/bin/gcc.elf
+	cp ../toolchain/native-gcc/sdk/bin/g++ $(BINDIR)/sdk/bin/g++.elf
+	cp ../toolchain/native-gcc/sdk/bin/cpp $(BINDIR)/sdk/bin/cpp.elf
+	mkdir -p $(BINDIR)/sdk/libexec/gcc/x86_64-montauk/14.2.0
+	cp ../toolchain/native-gcc/sdk/libexec/gcc/x86_64-montauk/14.2.0/cc1 \
+	   ../toolchain/native-gcc/sdk/libexec/gcc/x86_64-montauk/14.2.0/cc1plus \
+	   ../toolchain/native-gcc/sdk/libexec/gcc/x86_64-montauk/14.2.0/collect2 \
+	   $(BINDIR)/sdk/libexec/gcc/x86_64-montauk/14.2.0/
+	cp -r ../toolchain/native-gcc/sdk/lib/gcc $(BINDIR)/sdk/lib/gcc
+	cp ../toolchain/local/lib/gcc/x86_64-montauk/14.2.0/libgcc.a \
+	   ../toolchain/local/lib/gcc/x86_64-montauk/14.2.0/crtbegin.o \
+	   ../toolchain/local/lib/gcc/x86_64-montauk/14.2.0/crtend.o \
+	   $(BINDIR)/sdk/lib/gcc/x86_64-montauk/14.2.0/
+	cp ../toolchain/native/sdk/bin/ld $(BINDIR)/sdk/libexec/gcc/x86_64-montauk/14.2.0/ld
+	mkdir -p $(BINDIR)/tmp
+	printf 'scratch space for compiler intermediates\n' > $(BINDIR)/tmp/readme.txt
+else
+	@echo "devkit: toolchain/native-gcc/ not built; skipping native GCC"
+endif
 else
 	@echo "devkit: toolchain/native/ not built; skipping native dev tools"
 endif

programs/include/libc/ctype.h

@@ -16,6 +16,9 @@ int islower(int c);
 int isprint(int c);
 int ispunct(int c);
 int isxdigit(int c);
+
+#define isascii(c) (((c) & ~0x7F) == 0)
+#define toascii(c) ((c) & 0x7F)
 int iscntrl(int c);
 int isgraph(int c);
 int toupper(int c);

programs/include/libc/stdio.h

@@ -1,6 +1,12 @@
 #ifndef _LIBC_STDIO_H
 #define _LIBC_STDIO_H
 
+/* Conventional guard marker: packages like GMP sniff the libc's stdio
+   include-guard name to detect that FILE is available. */
+#ifndef _STDIO_H
+#define _STDIO_H 1
+#endif
+
 #pragma once
 
 #include <stdarg.h>

programs/include/libc/stdlib.h

@@ -62,6 +62,8 @@ int                mkstemp(char *template_);
 char              *mktemp(char *template_);
 char              *realpath(const char *path, char *resolved);
 size_t             mbstowcs(wchar_t *dst, const char *src, size_t n);
+#define MB_CUR_MAX 1
+
 int                mblen(const char *s, size_t n);
 int                mbtowc(wchar_t *pwc, const char *s, size_t n);
 int                wctomb(char *s, wchar_t wc);

programs/include/libc/sys/mman.h

@@ -0,0 +1,41 @@
+#ifndef _LIBC_SYS_MMAN_H
+#define _LIBC_SYS_MMAN_H
+
+#pragma once
+
+#include <sys/types.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/*
+    * Anonymous-memory mmap over SYS_ALLOC. SYS_ALLOC returns
+    * page-aligned process memory, which is exactly what callers like
+    * GCC's page allocator need. File-backed mappings are not
+    * supported and fail with ENODEV.
+*/
+
+#define PROT_NONE  0
+#define PROT_READ  1
+#define PROT_WRITE 2
+#define PROT_EXEC  4
+
+#define MAP_SHARED    0x01
+#define MAP_PRIVATE   0x02
+#define MAP_FIXED     0x10
+#define MAP_ANONYMOUS 0x20
+#define MAP_ANON      MAP_ANONYMOUS
+
+#define MAP_FAILED ((void *)-1)
+
+void *mmap(void *addr, size_t length, int prot, int flags, int fd,
+           long offset);
+int   munmap(void *addr, size_t length);
+int   mprotect(void *addr, size_t length, int prot);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* _LIBC_SYS_MMAN_H */

programs/include/libc/sys/stat.h

@@ -39,18 +39,18 @@ extern "C" {
 #define S_IXOTH 0001
 
 struct stat {
-    unsigned long st_dev;
+    dev_t     st_dev;
-    unsigned long st_ino;
+    ino_t     st_ino;
-    mode_t        st_mode;
+    mode_t    st_mode;
-    unsigned long st_nlink;
+    nlink_t   st_nlink;
-    uid_t         st_uid;
+    uid_t     st_uid;
-    gid_t         st_gid;
+    gid_t     st_gid;
-    unsigned long st_size;
+    off_t     st_size;
-    unsigned long st_blksize;
+    blksize_t st_blksize;
-    unsigned long st_blocks;
+    blkcnt_t  st_blocks;
-    time_t        st_atime;
+    time_t    st_atime;
-    time_t        st_mtime;
+    time_t    st_mtime;
-    time_t        st_ctime;
+    time_t    st_ctime;
 };
 
 int    mkdir(const char *path, unsigned int mode);

programs/include/libc/sys/types.h

@@ -21,6 +21,13 @@ typedef unsigned int  mode_t;
 typedef unsigned int  uid_t;
 typedef unsigned int  gid_t;
 typedef long          time_t;
+typedef unsigned long ino_t;
+typedef unsigned long dev_t;
+typedef unsigned long nlink_t;
+typedef long          blkcnt_t;
+typedef long          blksize_t;
+typedef long          suseconds_t;
+typedef int           clockid_t;
 
 #ifdef __cplusplus
 }

programs/include/libc/unistd.h

@@ -39,6 +39,14 @@ int    execve(const char *path, char *const argv[], char *const envp[]);
 int    execvp(const char *file, char *const argv[]);
 int    pipe(int fds[2]);
 long   pathconf(const char *path, int name);
+int    getpagesize(void);
+long   sysconf(int name);
+
+/* sysconf() names (Linux numbering). */
+#define _SC_OPEN_MAX         4
+#define _SC_PAGESIZE         30
+#define _SC_PAGE_SIZE        30
+#define _SC_NPROCESSORS_ONLN 84
 
 /* pathconf() names (Linux numbering). */
 #define _PC_LINK_MAX  0

programs/lib/libc/libc.c

@@ -22,6 +22,7 @@
 #include <sys/stat.h>
 #include <utime.h>
 #include <spawn.h>
+#include <sys/mman.h>
 #include <sys/time.h>
 #include <unistd.h>
 
@@ -2286,7 +2287,7 @@ int stat(const char *path, struct stat *buf) {
     int h = (int)_zos_syscall1(SYS_OPEN, (long)path);
     if (h >= 0) {
         buf->st_mode = S_IFREG;
-        buf->st_size = (unsigned long)_zos_syscall1(SYS_GETSIZE, (long)h);
+        buf->st_size = (off_t)_zos_syscall1(SYS_GETSIZE, (long)h);
         _zos_syscall1(SYS_CLOSE, (long)h);
         /* No inodes in the VFS API: derive a stable id from the path
            so that distinct paths compare as distinct files. */
@@ -2297,7 +2298,7 @@ int stat(const char *path, struct stat *buf) {
         buf->st_ino = ino | 1;
         buf->st_nlink = 1;
         buf->st_blksize = 4096;
-        buf->st_blocks = (buf->st_size + 511) / 512;
+        buf->st_blocks = (blkcnt_t)((buf->st_size + 511) / 512);
         return 0;
     }
 
@@ -2318,13 +2319,13 @@ int fstat(int fd, struct stat *buf) {
     }
     memset(buf, 0, sizeof(*buf));
     buf->st_mode = S_IFREG;
-    buf->st_size = (unsigned long)_zos_syscall1(SYS_GETSIZE, (long)fd);
+    buf->st_size = (off_t)_zos_syscall1(SYS_GETSIZE, (long)fd);
     /* Handles do not map back to paths, so fake a per-handle inode in a
        range disjoint from the path hashes used by stat(). */
     buf->st_ino = 0x4000000000000000UL + (unsigned long)fd;
     buf->st_nlink = 1;
     buf->st_blksize = 4096;
-    buf->st_blocks = (buf->st_size + 511) / 512;
+    buf->st_blocks = (blkcnt_t)((buf->st_size + 511) / 512);
     return 0;
 }
 
@@ -3711,6 +3712,57 @@ int kill(pid_t pid, int sig) {
     return 0;
 }
 
+int getpagesize(void) {
+    return 4096;
+}
+
+long sysconf(int name) {
+    switch (name) {
+    case 4:    /* _SC_OPEN_MAX */
+        return 64;
+    case 30:   /* _SC_PAGESIZE */
+        return 4096;
+    case 84:   /* _SC_NPROCESSORS_ONLN */
+        return 1;
+    default:
+        errno = EINVAL;
+        return -1;
+    }
+}
+
+/* Anonymous mappings only: SYS_ALLOC hands back zeroed page-aligned
+   memory and SYS_FREE releases it. Length is remembered by the kernel
+   per allocation, so munmap ignores its length argument. */
+void *mmap(void *addr, size_t length, int prot, int flags, int fd,
+           long offset) {
+    (void)addr; (void)prot; (void)offset;
+    if (length == 0 || fd != -1 || !(flags & MAP_ANONYMOUS)) {
+        errno = ENODEV;
+        return MAP_FAILED;
+    }
+    void *p = (void *)_zos_syscall1(SYS_ALLOC, (long)length);
+    if (p == NULL) {
+        errno = ENOMEM;
+        return MAP_FAILED;
+    }
+    return p;
+}
+
+int munmap(void *addr, size_t length) {
+    (void)length;
+    if (addr == NULL || addr == MAP_FAILED) {
+        errno = EINVAL;
+        return -1;
+    }
+    _zos_syscall1(SYS_FREE, (long)addr);
+    return 0;
+}
+
+int mprotect(void *addr, size_t length, int prot) {
+    (void)addr; (void)length; (void)prot;
+    return 0;   /* page protections are not adjustable from userspace */
+}
+
 long pathconf(const char *path, int name) {
     (void)path;
     switch (name) {

toolchain/README.md

@@ -80,6 +80,44 @@ make install-strip-gas install-strip-ld install-strip-binutils \
     DESTDIR=$PWD/../../native
 ```
 
+## Native GCC (runs on MontaukOS)
+
+GCC itself cross-builds for the montauk host (build dir
+toolchain/build/gcc-native, install DESTDIR toolchain/native-gcc):
+
+```bash
+../../src/gcc-14.2.0/configure \
+    --build=x86_64-pc-linux-gnu --host=x86_64-montauk \
+    --target=x86_64-montauk --prefix=/sdk \
+    --with-native-system-header-dir=/sdk/include \
+    --with-build-sysroot=$PWD/../../sysroot \
+    --enable-languages=c,c++ --disable-nls --disable-shared \
+    --disable-multilib --disable-gcov --disable-lto --disable-plugin \
+    --disable-bootstrap --disable-fixincludes --with-newlib \
+    --enable-initfini-array --disable-wchar_t --disable-libstdcxx-pch \
+    --with-gnu-as --with-gnu-ld
+ac_cv_c_bigendian=no make -j$(nproc) all-gcc
+make install-gcc DESTDIR=$PWD/../../native-gcc
+```
+
+Host-build gotchas, in the order they bite:
+- The bundled gmp/mpfr/mpc/isl/gettext carry their own config.sub
+  copies; overwrite each with the patched top-level one.
+- Remove the src tree's gettext symlink (--disable-nls does not skip
+  it, and its gnulib needs more locale surface than the libc has).
+- gmp.h sniffs the libc's stdio include-guard name to detect FILE;
+  the Montauk stdio.h defines the conventional _STDIO_H marker.
+- The gcc subdir configure cannot run host binaries to probe
+  endianness; preset ac_cv_c_bigendian=no.
+- The build sysroot needs an sdk -> usr symlink so
+  --with-native-system-header-dir=/sdk/include resolves at build time.
+
+The devkit target ships gcc/g++/cpp as .elf in 0:/sdk/bin, cc1 +
+cc1plus + collect2 (and a copy of ld for collect2's search) under
+0:/sdk/libexec/gcc/x86_64-montauk/14.2.0, libgcc.a + crtbegin/crtend
+under 0:/sdk/lib/gcc/x86_64-montauk/14.2.0, and a 0:/tmp scratch dir
+for driver intermediates.
+
 Notes:
 - Build only `all-gas all-ld all-binutils`. gprof needs fscanf with
   %[] scansets (not in the Montauk libc); gold and gprofng are