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regex: add regexec_buf() that can work on a non NUL-terminated string

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We just introduced a test that demonstrates that our sloppy use of
regexec() on a mmap()ed area can result in incorrect results or even
hard crashes.

So what we need to fix this is a function that calls regexec() on a
length-delimited, rather than a NUL-terminated, string.

Happily, there is an extension to regexec() introduced by the NetBSD
project and present in all major regex implementation including
Linux', MacOSX' and the one Git includes in compat/regex/: by using
the (non-POSIX) REG_STARTEND flag, it is possible to tell the
regexec() function that it should only look at the offsets between
pmatch[0].rm_so and pmatch[0].rm_eo.

That is exactly what we need.

Since support for REG_STARTEND is so widespread by now, let's just
introduce a helper function that always uses it, and tell people
on a platform whose regex library does not support it to use the
one from our compat/regex/ directory.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Johannes Schindelin 2016-09-21 20:24:04 +02:00 committed by Junio C Hamano
parent db5dfa3314
commit 2f8952250a
2 changed files with 15 additions and 1 deletions
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3
Makefile
View File

@ -296,7 +296,8 @@ all::
# Define USE_NED_ALLOCATOR if you want to replace the platforms default
# memory allocators with the nedmalloc allocator written by Niall Douglas.
#
# Define NO_REGEX if you have no or inferior regex support in your C library.
# Define NO_REGEX if your C library lacks regex support with REG_STARTEND
# feature.
#
# Define HAVE_DEV_TTY if your system can open /dev/tty to interact with the
# user.

13
git-compat-util.h
View File

@ -942,6 +942,19 @@ void git_qsort(void *base, size_t nmemb, size_t size,
#define qsort git_qsort
#endif
#ifndef REG_STARTEND
#error "Git requires REG_STARTEND support. Compile with NO_REGEX=NeedsStartEnd"
#endif
static inline int regexec_buf(const regex_t *preg, const char *buf, size_t size,
size_t nmatch, regmatch_t pmatch[], int eflags)
{
assert(nmatch > 0 && pmatch);
pmatch[0].rm_so = 0;
pmatch[0].rm_eo = size;
return regexec(preg, buf, nmatch, pmatch, eflags | REG_STARTEND);
}
#ifndef DIR_HAS_BSD_GROUP_SEMANTICS
# define FORCE_DIR_SET_GID S_ISGID
#else