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Portable implementation of snprintf(3), vsnprintf(3), asprintf(3), and vasprintf(3)
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weiss/c99-snprintf
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README file for C99-snprintf ============================ OVERVIEW -------- C99-snprintf provides a portable implementation of snprintf(3), vsnprintf(3), asprintf(3), and vasprintf(3). It should be fully C99 compliant, with the exceptions that it doesn't provide wide character support and that "%a" and "%A" conversions aren't supported. C99-snprintf should be buildable with any ANSI C compiler, it doesn't require libc functionality other than malloc(3) (for vasprintf(3)) and the stdarg(3) or varargs(3) macros, and it has no other prerequisites. The snprintf(3) and vsnprintf(3) functions are part of the C99 standard library. However, snprintf(3) and vsnprintf(3) weren't included in the C89/C90 standards and some systems don't provide C99 compliant implementations of these functions. For example, if the ouput buffer isn't big enough to hold the full conversion result, IRIX up to the current release 6.5.30 and glibc up to 2.0.x don't return the same value as with a sufficiently sized buffer (which makes it impossible to precompute the required buffer size), and some older systems (such as 64-bit Solaris 7) ignore the specified buffer size and overrun the buffer if it's too small. The asprintf(3) and vasprintf(3) functions aren't standardized at all. They're included with recent releases of glibc and BSD's libc, but they aren't available on other systems, such as System V (e.g., Solaris). So, if any of these functions are used, portable software should include replacement code which is used in case the functions aren't available or don't work correctly on the target system. C99-snprintf can be included with software packages in order to provide such replacement functions. USAGE ----- 1) Add snprintf.c to your project files. If you're using GNU Automake, you could use a line such as "foo_LDADD = $(LIBOBJS)" (where "foo" is the name of your program) in your Makefile.am. 2) Add snprintf.m4 to your m4 include directory or to your acinclude.m4 file. If you're using neither, you can simply include the contents of snprintf.m4 in your configure.ac file. 3) For each replacement function which might be needed in your project, call the according Autoconf macro in your configure.ac file. That is, in order to have all four replacement functions available if needed: HW_FUNC_VSNPRINTF HW_FUNC_SNPRINTF HW_FUNC_VASPRINTF HW_FUNC_ASPRINTF 4) The required replacement functions should be declared in some header file included throughout your project files: #if HAVE_CONFIG_H #include <config.h> #endif #if HAVE_STDARG_H #include <stdarg.h> #if !HAVE_VSNPRINTF int rpl_vsnprintf(char *, size_t, const char *, va_list); #endif #if !HAVE_SNPRINTF int rpl_snprintf(char *, size_t, const char *, ...); #endif #if !HAVE_VASPRINTF int rpl_vasprintf(char **, const char *, va_list); #endif #if !HAVE_ASPRINTF int rpl_asprintf(char **, const char *, ...); #endif #endif /* HAVE_STDARG_H */ USAGE WITHOUT GNU AUTOCONF -------------------------- If you're not using GNU Autoconf, omit the steps 2 and 3 from the above instructions. Instead: 1) The following preprocessor macros should be defined to 1 if the feature or file in question is available on the target system (though basic functionality should be available as long as HAVE_STDARG_H is defined correctly): HAVE_VSNPRINTF HAVE_SNPRINTF HAVE_VASPRINTF HAVE_ASPRINTF HAVE_STDARG_H HAVE_STDDEF_H HAVE_STDINT_H HAVE_STDLIB_H HAVE_FLOAT_H HAVE_INTTYPES_H HAVE_LOCALE_H HAVE_LOCALECONV HAVE_LCONV_DECIMAL_POINT HAVE_LCONV_THOUSANDS_SEP HAVE_LONG_DOUBLE HAVE_LONG_LONG_INT HAVE_UNSIGNED_LONG_LONG_INT HAVE_INTMAX_T HAVE_UINTMAX_T HAVE_UINTPTR_T HAVE_PTRDIFF_T HAVE_VA_COPY HAVE___VA_COPY 2) The calls to the functions which should be replaced must be redefined throughout the project files: #define vsnprintf rpl_vsnprintf #define snprintf rpl_snprintf #define vasprintf rpl_vasprintf #define asprintf rpl_asprintf BUGS AND CAVEATS ---------------- Depending on the size of the largest integer type available on the target platform, floating point precisions larger than 9, 19, or 38 are not supported. If a larger precision is specified, it will silently be reduced to the largest possible precision on the target system. If the integral part of a floating point value doesn't fit into the largest integer type available on the target platform, the conversion will fail. In this case, C99-snprintf will return -1 and set the global variable errno to indicate the error. The same is done if the specified field width or precision are (or if the return value would be) larger than INT_MAX. C99-snprintf makes a few assumptions regarding integer (and pointer value) conversions which aren't backed by the C standard, but which should be safe in practice. FEEDBACK -------- Please let me know if you have any comments or bug reports regarding C99-snprintf: Holger Weiss <holger@jhweiss.de> # vim: set joinspaces textwidth=72 filetype=none:
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Portable implementation of snprintf(3), vsnprintf(3), asprintf(3), and vasprintf(3)
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