https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109609
--- Comment #17 from Gabriel Burca <gburca-gnu at ebixio dot com> --- Speaking of the size parameter, my workaround for the original issue was to pre-compute the size argument a different way. This however resulted in a warning that's both right and wrong. Here's the sample code that must be compiled with -O3 and -Wall: https://godbolt.org/z/jbf74994z ``` static constexpr unsigned N = 20; char dst[N + 1]; int main() { char buf[10]; char *src = buf + sizeof(buf); *(--src) = 0; *(--src) = 'a'; strncpy(dst, src, std::min<size_t>(N, strlen(src) + 1)); // constexpr volatile size_t n = std::min<size_t>(N, strlen(src) + 1); // strncpy(dst, src, n); } ``` <source>: In function 'int main()': <source>:13:10: warning: 'char* strncpy(char*, const char*, size_t)' specified bound depends on the length of the source argument [-Wstringop-truncation] 13 | strncpy(dst, src, std::min<size_t>(N, strlen(src) + 1)); | ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ <source>:13:47: note: length computed here 13 | strncpy(dst, src, std::min<size_t>(N, strlen(src) + 1)); | ~~~~~~^~~~~ Sure, it depends on the src, but in a "good" way. The commented out code doesn't produce the warning. An alternative way to make the warning go away is to change to: char *src = buf + sizeof(buf) - 1;
