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macro: handle overflow in ALIGN_TO() somewhat reasonably

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The helper call rounds up to next multiple of specified boundary. If one
passes a very large value as first argument, then there might not be a
next multiple. So far we ignored that. Let's handle this now and return
SIZE_MAX in this case, as special indicator that we reached the end.

Of course, IRL this should not happen. With this new change we at least
do something somewhat reasonable, leaving it to the caller to handle it
further.
This commit is contained in:
Lennart Poettering 2021-08-20 18:11:14 +02:00
parent eeed637fea
commit c7ed718720
2 changed files with 47 additions and 0 deletions
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14
src/basic/macro.h
View File

@ -146,6 +146,20 @@
#define ALIGN8_PTR(p) ((void*) ALIGN8((unsigned long) (p)))
static inline size_t ALIGN_TO(size_t l, size_t ali) {
/* Check that alignment is exponent of 2 */
#if SIZE_MAX == UINT_MAX
assert(__builtin_popcount(ali) == 1);
#elif SIZE_MAX == ULONG_MAX
assert(__builtin_popcountl(ali) == 1);
#elif SIZE_MAX == ULONGLONG_MAX
assert(__builtin_popcountll(ali) == 1);
#else
#error "Unexpected size_t"
#endif
if (l > SIZE_MAX - (ali - 1))
return SIZE_MAX; /* indicate overflow */
return ((l + ali - 1) & ~(ali - 1));
}

33
src/test/test-macro.c
View File

@ -295,6 +295,38 @@ static void test_foreach_pointer(void) {
assert(k == 11);
}
static void test_align_to(void) {
log_info("/* %s */", __func__);
assert_se(ALIGN_TO(0, 1) == 0);
assert_se(ALIGN_TO(1, 1) == 1);
assert_se(ALIGN_TO(2, 1) == 2);
assert_se(ALIGN_TO(3, 1) == 3);
assert_se(ALIGN_TO(4, 1) == 4);
assert_se(ALIGN_TO(SIZE_MAX-1, 1) == SIZE_MAX-1);
assert_se(ALIGN_TO(SIZE_MAX, 1) == SIZE_MAX);
assert_se(ALIGN_TO(0, 2) == 0);
assert_se(ALIGN_TO(1, 2) == 2);
assert_se(ALIGN_TO(2, 2) == 2);
assert_se(ALIGN_TO(3, 2) == 4);
assert_se(ALIGN_TO(4, 2) == 4);
assert_se(ALIGN_TO(SIZE_MAX-3, 2) == SIZE_MAX-3);
assert_se(ALIGN_TO(SIZE_MAX-2, 2) == SIZE_MAX-1);
assert_se(ALIGN_TO(SIZE_MAX-1, 2) == SIZE_MAX-1);
assert_se(ALIGN_TO(SIZE_MAX, 2) == SIZE_MAX); /* overflow */
assert_se(ALIGN_TO(0, 4) == 0);
assert_se(ALIGN_TO(1, 4) == 4);
assert_se(ALIGN_TO(2, 4) == 4);
assert_se(ALIGN_TO(3, 4) == 4);
assert_se(ALIGN_TO(4, 4) == 4);
assert_se(ALIGN_TO(SIZE_MAX-3, 4) == SIZE_MAX-3);
assert_se(ALIGN_TO(SIZE_MAX-2, 4) == SIZE_MAX); /* overflow */
assert_se(ALIGN_TO(SIZE_MAX-1, 4) == SIZE_MAX); /* overflow */
assert_se(ALIGN_TO(SIZE_MAX, 4) == SIZE_MAX); /* overflow */
}
int main(int argc, char *argv[]) {
test_setup_logging(LOG_INFO);
@ -305,6 +337,7 @@ int main(int argc, char *argv[]) {
test_in_set();
test_foreach_pointer();
test_ptr_to_int();
test_align_to();
return 0;
}