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authorMax Filippov <jcmvbkbc@gmail.com>2018-01-09 00:48:31 -0800
committerWaldemar Brodkorb <wbx@uclibc-ng.org>2018-01-15 20:01:44 +0000
commitae1b43635802dccd9fc793474c433b5dca23841f (patch)
treeea03255aabc2427bee894f6fc68cd7492b5ce06c /docs
parentae56f3a633860a984d42dd9a6959e1d5983296e5 (diff)
xtensa: fix strcmp
Loops with 'loop forever' annotation inside strcmp are actually meant to loop forever. Falling through the end of the first loop may result in equal strings being compared unequal, e.g.: #include <string.h> int main(void) { char a[4096] __attribute__((aligned(4))); char b[4096] __attribute__((aligned(4))); memset(a, ' ', 258 * 8); memset(b, ' ', 258 * 8); a[255 * 8] = 0; a[256 * 8] = 'a'; b[255 * 8] = 0; b[256 * 8] = 'b'; return !(strcmp(a, b) == 0); } Falling through the end of the second loop may result in unequal strings being compared as equal, e.g.: #include <string.h> int main(void) { char a[4096] __attribute__((aligned(4))); char b[4096] __attribute__((aligned(4))); memset(a, ' ', 514 * 6); memset(b, ' ', 514 * 6); a[514 * 6 + 0] = 'a'; a[514 * 6 + 1] = 0; b[514 * 6 + 0] = 'b'; b[514 * 6 + 1] = 0; return !(strcmp(a, b) != 0); } Use 0 as a loop counter to make 2^32 - 1 iterations which is enough to cover all addressable memory. While at it drop useless nop at the end of the first loop and use a11 for all loop counters. Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
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