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tree-wide: make new/new0/malloc_multiply/reallocarray safe for size 0

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All underlying glibc calls are free to return NULL if the size argument
is 0. We most often call those functions with a fixed argument, or at least
something which obviously cannot be zero, but it's too easy to forget.

E.g. coverity complains about "rows = new0(JsonVariant*, n_rows-1);" in
format-table.c There is an assert that n_rows > 0, so we could hit this
corner case here. Let's simplify callers and make those functions "safe".

CID #1397035.

The compiler is mostly able to optimize this away:
$ size build{,-opt}/src/shared/libsystemd-shared-239.so
(before)
   text	   data	    bss	    dec	    hex	filename
2643329	 580940	   3112	3227381	 313ef5	build/src/shared/libsystemd-shared-239.so     (-O0 -g)
2170013	 578588	   3089	2751690	 29fcca	build-opt/src/shared/libsystemd-shared-239.so (-03 -flto -g)
(after)
   text	   data	    bss	    dec	    hex	filename
2644017	 580940	   3112	3228069	 3141a5	build/src/shared/libsystemd-shared-239.so
2170765	 578588	   3057	2752410	 29ff9a	build-opt/src/shared/libsystemd-shared-239.so
This commit is contained in:
Zbigniew Jędrzejewski-Szmek 2018-12-21 10:21:41 +01:00 committed by Lennart Poettering
parent 5f9026027d
commit 830464c3e4
2 changed files with 4 additions and 4 deletions
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2
src/basic/alloc-util.c
View File

@ -12,7 +12,7 @@ void* memdup(const void *p, size_t l) {
assert(l == 0 || p);
ret = malloc(l);
ret = malloc(l ?: 1);
if (!ret)
return NULL;

6
src/basic/alloc-util.h
View File

@ -12,7 +12,7 @@ typedef void (*free_func_t)(void *p);
#define new(t, n) ((t*) malloc_multiply(sizeof(t), (n)))
#define new0(t, n) ((t*) calloc((n), sizeof(t)))
#define new0(t, n) ((t*) calloc((n) ?: 1, sizeof(t)))
#define newa(t, n) \
({ \
@ -77,7 +77,7 @@ _malloc_ _alloc_(1, 2) static inline void *malloc_multiply(size_t size, size_t
if (size_multiply_overflow(size, need))
return NULL;
return malloc(size * need);
return malloc(size * need ?: 1);
}
#if !HAVE_REALLOCARRAY
@ -85,7 +85,7 @@ _alloc_(2, 3) static inline void *reallocarray(void *p, size_t need, size_t size
if (size_multiply_overflow(size, need))
return NULL;
return realloc(p, size * need);
return realloc(p, size * need ?: 1);
}
#endif