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add QSORT

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Add the macro QSORT, a convenient wrapper for qsort(3) that infers the
size of the array elements and supports the convention of initializing
empty arrays with a NULL pointer, which we use in some places.

Calling qsort(3) directly with a NULL pointer is undefined -- even with
an element count of zero -- and allows the compiler to optimize away any
following NULL checks.  Using the macro avoids such surprises.

Add a semantic patch as well to demonstrate the macro's usage and to
automate the transformation of trivial cases.

Signed-off-by: Rene Scharfe <l.s.r@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
René Scharfe
2016-09-29 17:23:43 +02:00
committed by Junio C Hamano
parent 21f862b498
commit dbc540c7a5
2 changed files with 27 additions and 0 deletions
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8
git-compat-util.h
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@ -977,6 +977,14 @@ void git_qsort(void *base, size_t nmemb, size_t size,
#define qsort git_qsort
#endif
#define QSORT(base, n, compar) sane_qsort((base), (n), sizeof(*(base)), compar)
static inline void sane_qsort(void *base, size_t nmemb, size_t size,
int(*compar)(const void *, const void *))
{
if (nmemb > 1)
qsort(base, nmemb, size, compar);
}
#ifndef REG_STARTEND
#error "Git requires REG_STARTEND support. Compile with NO_REGEX=NeedsStartEnd"
#endif