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a9bfbc5b69
If you define SNPRINTF_RETURNS_BOGUS, we use a special git_vsnprintf wrapper assumes that vsnprintf returns "-1" instead of the number of characters that you would need to store the result. To do this, it invokes vsnprintf multiple times, growing a heap buffer until we have enough space to hold the result. However, this means we evaluate the va_list parameter multiple times, which is generally a bad thing (it may be modified by calls to vsnprintf, yielding undefined behavior). Instead, we must va_copy it and hand the copy to vsnprintf, so we always have a pristine va_list. Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
69 lines
1.5 KiB
C
69 lines
1.5 KiB
C
#include "../git-compat-util.h"
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/*
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* The size parameter specifies the available space, i.e. includes
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* the trailing NUL byte; but Windows's vsnprintf uses the entire
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* buffer and avoids the trailing NUL, should the buffer be exactly
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* big enough for the result. Defining SNPRINTF_SIZE_CORR to 1 will
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* therefore remove 1 byte from the reported buffer size, so we
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* always have room for a trailing NUL byte.
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*/
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#ifndef SNPRINTF_SIZE_CORR
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#if defined(WIN32) && (!defined(__GNUC__) || __GNUC__ < 4)
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#define SNPRINTF_SIZE_CORR 1
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#else
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#define SNPRINTF_SIZE_CORR 0
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#endif
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#endif
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#undef vsnprintf
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int git_vsnprintf(char *str, size_t maxsize, const char *format, va_list ap)
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{
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va_list cp;
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char *s;
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int ret = -1;
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if (maxsize > 0) {
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va_copy(cp, ap);
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ret = vsnprintf(str, maxsize-SNPRINTF_SIZE_CORR, format, cp);
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va_end(cp);
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if (ret == maxsize-1)
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ret = -1;
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/* Windows does not NUL-terminate if result fills buffer */
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str[maxsize-1] = 0;
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}
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if (ret != -1)
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return ret;
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s = NULL;
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if (maxsize < 128)
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maxsize = 128;
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while (ret == -1) {
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maxsize *= 4;
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str = realloc(s, maxsize);
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if (! str)
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break;
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s = str;
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va_copy(cp, ap);
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ret = vsnprintf(str, maxsize-SNPRINTF_SIZE_CORR, format, cp);
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va_end(cp);
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if (ret == maxsize-1)
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ret = -1;
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}
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free(s);
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return ret;
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}
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int git_snprintf(char *str, size_t maxsize, const char *format, ...)
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{
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va_list ap;
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int ret;
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va_start(ap, format);
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ret = git_vsnprintf(str, maxsize, format, ap);
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va_end(ap);
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return ret;
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}
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