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git-compat-util: introduce more size_t helpers 

We will use them in the next commit.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
maint
Johannes Schindelin 2021-11-02 15:46:09 +00:00 committed by Junio C Hamano
parent e9aa762cc7
commit e2ffeae3f6
1 changed files with 25 additions and 0 deletions
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25
git-compat-util.h
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@ -113,6 +113,14 @@
#define unsigned_mult_overflows(a, b) \
((a) && (b) > maximum_unsigned_value_of_type(a) / (a))

/*
* Returns true if the left shift of "a" by "shift" bits will
* overflow. The type of "a" must be unsigned.
*/
#define unsigned_left_shift_overflows(a, shift) \
((shift) < bitsizeof(a) && \
(a) > maximum_unsigned_value_of_type(a) >> (shift))

#ifdef __GNUC__
#define TYPEOF(x) (__typeof__(x))
#else
@ -859,6 +867,23 @@ static inline size_t st_sub(size_t a, size_t b)
return a - b;
}

static inline size_t st_left_shift(size_t a, unsigned shift)
{
if (unsigned_left_shift_overflows(a, shift))
die("size_t overflow: %"PRIuMAX" << %u",
(uintmax_t)a, shift);
return a << shift;
}

static inline unsigned long cast_size_t_to_ulong(size_t a)
{
if (a != (unsigned long)a)
die("object too large to read on this platform: %"
PRIuMAX" is cut off to %lu",
(uintmax_t)a, (unsigned long)a);
return (unsigned long)a;
}

#ifdef HAVE_ALLOCA_H
# include <alloca.h>
# define xalloca(size) (alloca(size))