feat: hosted libstdc++ for x86_64-montauk - full C++ on MontaukOS

The cross toolchain now builds real hosted C++: std::string, vector,
unique_ptr, iostreams and exceptions all work in a plain
x86_64-montauk-g++ invocation with no special flags. This is the
library that native cc1plus will link against for the GCC self-host.

crt1 now runs .preinit_array/.init_array before main and hooks
.fini_array through atexit (main returns via exit(), so destructors
run on both exit paths). Global constructors and libgcc's eh_frame
registration both ride this. GCC is reconfigured with
--enable-initfini-array (modern arrays instead of .ctors),
--with-newlib (satisfies libstdc++'s crossconfig for unknown hosts),
--disable-wchar_t and --disable-libstdcxx-pch; the montauk gcc patch
grows a hunk keeping os/generic ctype under --with-newlib (the
Montauk libc is not newlib).

libc additions harvested by the libstdc++ build: mbtowc/wctomb,
strxfrm, strtok/strtok_r, a real vfscanf/fscanf/scanf (character-
driven with widths and l/ll; also unblocks gprof later), fgetpos/
fsetpos/setbuf/fpos_t, modf plus the C99 float math variants
(acosf..tanhf, hypot/hypotf as wrappers), FP_* classification macros,
the full POSIX errno vocabulary, complete DT_* dirent types, and
mbstate_t.

The SDK ships the real libstdc++.a (was an empty stand-in), the C++
headers at 0:/sdk/include/c++, and cxx-test.elf (global ctor, string,
vector+sort, unique_ptr, throw/catch; exits 0 on 5/5). Ramdisk sits
at 1571 files, within the 2048 table.

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

programs/include/libc/dirent.h

@@ -9,8 +9,13 @@ extern "C" {
 
 #define NAME_MAX   255
 #define DT_UNKNOWN 0
+#define DT_FIFO    1
+#define DT_CHR     2
 #define DT_DIR     4
+#define DT_BLK     6
 #define DT_REG     8
+#define DT_LNK     10
+#define DT_SOCK    12
 
 struct dirent {
     unsigned char d_type;

programs/include/libc/errno.h

@@ -49,8 +49,47 @@ extern int errno;
 #define ENOTEMPTY    39
 #define ELOOP        40
 #define EWOULDBLOCK  EAGAIN
+#define ETXTBSY      26
+#define ENOMSG       42
+#define EIDRM        43
+#define ENOSTR       60
+#define ENODATA      61
+#define ETIME        62
+#define ENOSR        63
+#define ENOLINK      67
+#define EPROTO       71
+#define EMULTIHOP    72
+#define EBADMSG      74
 #define EOVERFLOW    75
+#define EILSEQ       84
+#define ENOTSOCK     88
+#define EDESTADDRREQ 89
+#define EMSGSIZE     90
+#define EPROTOTYPE   91
+#define ENOPROTOOPT  92
+#define EPROTONOSUPPORT 93
+#define EOPNOTSUPP   95   /* == ENOTSUP, Linux numbering */
+#define EAFNOSUPPORT 97
+#define EADDRINUSE   98
+#define EADDRNOTAVAIL 99
+#define ENETDOWN     100
+#define ENETUNREACH  101
+#define ENETRESET    102
+#define ECONNABORTED 103
+#define ECONNRESET   104
+#define ENOBUFS      105
+#define EISCONN      106
+#define ENOTCONN     107
 #define ETIMEDOUT    110
+#define ECONNREFUSED 111
+#define EHOSTUNREACH 113
+#define EALREADY     114
+#define EINPROGRESS  115
+#define ESTALE       116
+#define EDQUOT       122
+#define ECANCELED    125
+#define EOWNERDEAD   130
+#define ENOTRECOVERABLE 131
 #define ENOTSUP      95
 
 #ifdef __cplusplus

programs/include/libc/math.h

@@ -11,8 +11,47 @@ extern "C" {
 #define INFINITY  __builtin_inff()
 #define NAN       __builtin_nanf("")
 
+/* C99 floating-point classification. */
+#define FP_NAN       0
+#define FP_INFINITE  1
+#define FP_ZERO      2
+#define FP_SUBNORMAL 3
+#define FP_NORMAL    4
+
+#define fpclassify(x) \
+    __builtin_fpclassify(FP_NAN, FP_INFINITE, FP_NORMAL, FP_SUBNORMAL, \
+                         FP_ZERO, x)
+#define isnan(x)    __builtin_isnan(x)
+#define isinf(x)    __builtin_isinf(x)
+#define isfinite(x) __builtin_isfinite(x)
+#define isnormal(x) __builtin_isnormal(x)
+#define signbit(x)  __builtin_signbit(x)
+
 double fabs(double x);
 double frexp(double x, int *exp);
+
+/* C89 modf and the C99 float variants assumed by hosted libstdc++
+   (--with-newlib crossconfig). The float forms wrap the double
+   implementations. */
+double modf(double x, double *iptr);
+float  modff(float x, float *iptr);
+double hypot(double x, double y);
+float  hypotf(float x, float y);
+float  acosf(float x);
+float  asinf(float x);
+float  atanf(float x);
+float  atan2f(float y, float x);
+float  coshf(float x);
+float  expf(float x);
+float  fmodf(float x, float y);
+float  frexpf(float x, int *exp);
+float  ldexpf(float x, int exp);
+float  logf(float x);
+float  log10f(float x);
+float  powf(float x, float y);
+float  sinhf(float x);
+float  tanf(float x);
+float  tanhf(float x);
 double ldexp(double x, int n);
 long double ldexpl(long double x, int n);
 double floor(double x);

programs/include/libc/stdio.h

@@ -39,6 +39,15 @@ extern FILE *stderr;
 int    putc(int c, FILE *stream);
 void   rewind(FILE *stream);
 int    getchar(void);
+typedef long fpos_t;
+
+int    fgetpos(FILE *stream, fpos_t *pos);
+int    fsetpos(FILE *stream, const fpos_t *pos);
+void   setbuf(FILE *stream, char *buf);
+int    fscanf(FILE *stream, const char *fmt, ...);
+int    scanf(const char *fmt, ...);
+int    vfscanf(FILE *stream, const char *fmt, va_list ap);
+
 int    fileno(FILE *stream);
 FILE  *fdopen(int fd, const char *mode);
 

programs/include/libc/stdlib.h

@@ -63,6 +63,8 @@ char              *mktemp(char *template_);
 char              *realpath(const char *path, char *resolved);
 size_t             mbstowcs(wchar_t *dst, const char *src, size_t n);
 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);
 double        strtod(const char *nptr, char **endptr);
 float         strtof(const char *nptr, char **endptr);
 long double   strtold(const char *nptr, char **endptr);

programs/include/libc/string.h

@@ -31,6 +31,9 @@ char  *strpbrk(const char *s, const char *accept);
 int    strcasecmp(const char *s1, const char *s2);
 int    strncasecmp(const char *s1, const char *s2, size_t n);
 int    strcoll(const char *s1, const char *s2);
+size_t strxfrm(char *dest, const char *src, size_t n);
+char  *strtok(char *str, const char *delim);
+char  *strtok_r(char *str, const char *delim, char **saveptr);
 char  *strstr(const char *haystack, const char *needle);
 const char *strerror(int errnum);
 

programs/include/libc/wchar.h

@@ -11,6 +11,11 @@ extern "C" {
 
 typedef unsigned int wint_t;
 
+/* Opaque shift state for the (byte-oriented) C locale. */
+typedef struct {
+    unsigned long __opaque;
+} mbstate_t;
+
 #define WEOF ((wint_t)-1)
 
 /* Byte-oriented C locale only: one byte, one character. */