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Merge branch 'ep/do-not-feed-a-pointer-to-array-size' into maint

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Catch a programmer mistake to feed a pointer not an array to
ARRAY_SIZE() macro, by using a couple of GCC extensions.

* ep/do-not-feed-a-pointer-to-array-size:
  git-compat-util.h: implement a different ARRAY_SIZE macro for for safely deriving the size of array
This commit is contained in:
Junio C Hamano 2015-06-16 14:33:41 -07:00
commit 335f1a7eb2
1 changed files with 53 additions and 1 deletions
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54
git-compat-util.h
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@ -3,6 +3,23 @@
#define _FILE_OFFSET_BITS 64
/* Derived from Linux "Features Test Macro" header
* Convenience macros to test the versions of gcc (or
* a compatible compiler).
* Use them like this:
* #if GIT_GNUC_PREREQ (2,8)
* ... code requiring gcc 2.8 or later ...
* #endif
*/
#if defined(__GNUC__) && defined(__GNUC_MINOR__)
# define GIT_GNUC_PREREQ(maj, min) \
((__GNUC__ << 16) + __GNUC_MINOR__ >= ((maj) << 16) + (min))
#else
#define GIT_GNUC_PREREQ(maj, min) 0
#endif
#ifndef FLEX_ARRAY
/*
* See if our compiler is known to support flexible array members.
@ -25,7 +42,42 @@
#endif
#endif
#define ARRAY_SIZE(x) (sizeof(x)/sizeof(x[0]))
/*
* BUILD_ASSERT_OR_ZERO - assert a build-time dependency, as an expression.
* @cond: the compile-time condition which must be true.
*
* Your compile will fail if the condition isn't true, or can't be evaluated
* by the compiler. This can be used in an expression: its value is "0".
*
* Example:
* #define foo_to_char(foo) \
* ((char *)(foo) \
* + BUILD_ASSERT_OR_ZERO(offsetof(struct foo, string) == 0))
*/
#define BUILD_ASSERT_OR_ZERO(cond) \
(sizeof(char [1 - 2*!(cond)]) - 1)
#if defined(__GNUC__) && (__GNUC__ >= 3)
# if GIT_GNUC_PREREQ(3, 1)
/* &arr[0] degrades to a pointer: a different type from an array */
# define BARF_UNLESS_AN_ARRAY(arr) \
BUILD_ASSERT_OR_ZERO(!__builtin_types_compatible_p(__typeof__(arr), \
__typeof__(&(arr)[0])))
# else
# define BARF_UNLESS_AN_ARRAY(arr) 0
# endif
#endif
/*
* ARRAY_SIZE - get the number of elements in a visible array
* <at> x: the array whose size you want.
*
* This does not work on pointers, or arrays declared as [], or
* function parameters. With correct compiler support, such usage
* will cause a build error (see the build_assert_or_zero macro).
*/
#define ARRAY_SIZE(x) (sizeof(x) / sizeof((x)[0]) + BARF_UNLESS_AN_ARRAY(x))
#define bitsizeof(x) (CHAR_BIT * sizeof(x))
#define maximum_signed_value_of_type(a) \