diff options
| -rw-r--r-- | src/string.cpp | 40 |
1 files changed, 32 insertions, 8 deletions
diff --git a/src/string.cpp b/src/string.cpp index b6e40b7b3..a70b484bd 100644 --- a/src/string.cpp +++ b/src/string.cpp @@ -20,6 +20,10 @@ #include <stdarg.h> #include <ctype.h> /* required for tolower() */ +#ifdef _MSC_VER +#include <errno.h> // required by vsnprintf implementation for MSVC +#endif + /** * Safer implementation of vsnprintf; same as vsnprintf except: * - last instead of size, i.e. replace sizeof with lastof. @@ -219,17 +223,37 @@ int CDECL snprintf(char *str, size_t size, const char *format, ...) #endif /* MinGW Runtime < 3.14 */ #ifdef _MSC_VER -/* *nprintf broken, not POSIX compliant, MSDN description - * - If len < count, then len characters are stored in buffer, a null-terminator is appended, and len is returned. - * - If len = count, then len characters are stored in buffer, no null-terminator is appended, and len is returned. - * - If len > count, then count characters are stored in buffer, no null-terminator is appended, and a negative value is returned +/** + * Almost POSIX compliant implementation of \c vsnprintf for VC compiler. + * The difference is in the value returned on output truncation. This + * implementation returns size whereas a POSIX implementation returns + * size or more (the number of bytes that would be written to str + * had size been sufficiently large excluding the terminating null byte). */ int CDECL vsnprintf(char *str, size_t size, const char *format, va_list ap) { - int ret; - ret = _vsnprintf(str, size, format, ap); - if (ret < 0 || ret == size) str[size - 1] = '\0'; - return ret; + if (size == 0) return 0; + + errno = 0; + int ret = _vsnprintf(str, size, format, ap); + + if (ret < 0) { + if (errno != ERANGE) { + /* There's a formatting error, better get that looked + * at properly instead of ignoring it. */ + NOT_REACHED(); + } + } else if ((size_t)ret < size) { + /* The buffer is big enough for the number of + * characers stored (excluding null), i.e. + * the string has been null-terminated. */ + return ret; + } + + /* The buffer is too small for _vsnprintf to write the + * null-terminator at its end and return size. */ + str[size - 1] = '\0'; + return size; } #endif /* _MSC_VER */ |