https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100404
Bug ID: 100404 Summary: Unable to disable removal of null pointer checks for nonnull function arguments Product: gcc Version: 10.2.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: c Assignee: unassigned at gcc dot gnu.org Reporter: gccgc at bithub dot de Target Milestone: --- Based on the documentation of the "nonnull" function attribute "-fno-delete-null-pointer-checks" may be used to disable compiler optimizations based on the knowledge that a function argument cannot be null ([1]). However, on GCC 10.2 with optimization level 1 (and also on earlier versions with optimization level 2) the NULL check is eliminated from the following sample program: int __attribute__ ((nonnull)) isnull(char *ptr) { if (ptr == 0) return 0; return 1; } int main(void) { return isnull(0); } Compiling this sample without optimizations and "-fdelete-null-pointer-checks" does not eliminate the check so the optimization seems to be triggered by another optimization. [1] https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-nonnull-function-attribute