[PR32479] Avoid newlib vasprintf, since it requires gnu extensions

[bcraig]

Summary

Newlib 2.5 doesn't define vasprintf unless gnu extensions are turned on. So now, we provide our own implementation backed by vsnprintf.

[EricWF]

Why are GNU extensions not turned on? AFAIK Libc++ doesn't compile against any C library without GNU extensions enabled, including glibc and apple-libc.

[EricWF]

The bug relating to this patch was closed as WONTFIX. This review should be closed.

include/__bsd_locale_fallbacks.h

int __libcpp_snprintf_l(char *__s, size_t __n, locale_t __l, const char *__format, ...) {
     return __res;
 }
 
 inline
 int __libcpp_asprintf_l(char **__s, locale_t __l, const char *__format, ...) {
     va_list __va;
     va_start(__va, __format);
     __locale_raii __current( uselocale(__l), uselocale );
+#if _LIBCPP_HAS_NO_ASPRINTF
+    va_list __va2;
+    va_copy(__va2, __va);
+    int __res = vsnprintf(0, 0, __format, __va2);
+    va_end(__va2);
+    if(__res < 0)
+    {
+        va_end(__va);
+        return __res;
+    }
+    *__s = (char *)malloc(__res+1);
+    if(*__s == 0)
+    {
+        va_end(__va);
+        return -1;
+    }
+    vsnprintf(*__s, __res+1, __format, __va);
+#else
     int __res = vasprintf(__s, __format, __va);
+#endif
     va_end(__va);
     return __res;
 }
 
 inline
 int __libcpp_sscanf_l(const char *__s, locale_t __l, const char *__format, ...) {
     va_list __va;
     va_start(__va, __format);

include/__config

 
 #if defined(__unix__) || (defined(__APPLE__) && defined(__MACH__))
 // Most unix variants have catopen.  These are the specific ones that don't.
 #if !defined(__BIONIC__) && !defined(_NEWLIB_VERSION)
 #define _LIBCPP_HAS_CATOPEN 1
 #endif
 #endif
 
+#if defined(_NEWLIB_VERSION)
+#define _LIBCPP_HAS_NO_ASPRINTF 1
+#endif
+
 #ifdef __FreeBSD__
 #define _DECLARE_C99_LDBL_MATH 1
 #endif
 
 #if defined(__APPLE__)
 # if !defined(__MAC_OS_X_VERSION_MIN_REQUIRED) && \
      defined(__ENVIRONMENT_MAC_OS_X_VERSION_MIN_REQUIRED__)
 #   define __MAC_OS_X_VERSION_MIN_REQUIRED __ENVIRONMENT_MAC_OS_X_VERSION_MIN_REQUIRED__