https://gcc.gnu.org/bugzilla/show_bug.cgi?id=118867
--- Comment #15 from GCC Commits <cvs-commit at gcc dot gnu.org> --- The trunk branch has been updated by Andrew Pinski <pins...@gcc.gnu.org>: https://gcc.gnu.org/g:0c3cc57f0e71a7a945fb10c817260dd8a7894e7f commit r15-7547-g0c3cc57f0e71a7a945fb10c817260dd8a7894e7f Author: Andrew Pinski <quic_apin...@quicinc.com> Date: Thu Feb 13 14:10:06 2025 -0800 libstdc++: Improve list assumption after constructor [PR118865] The code example here does: ``` if (begin == end) __builtin_unreachable(); std::list nl(begin, end); for (auto it = nl.begin(); it != nl.end(); it++) { ... } /* Remove the first element of the list. */ nl.erase(nl.begin()); ``` And we get a warning because because we jump threaded the case were we think the list was empty from the for loop BUT we populated it without an empty array. So can help the compiler here by adding that after initializing the list with non empty array, that the list will not be empty either. This is able to remove the -Wfree-nonheap-object warning in the first reduced testcase (with the fix for `begin == end` case added) in the PR 118865; the second reduced testcase has been filed off as PR 118867. Bootstrapped and tested on x86_64-linux-gnu. libstdc++-v3/ChangeLog: PR libstdc++/118865 * include/bits/stl_list.h (_M_initialize_dispatch): Add an unreachable if the iterator was not empty that the list will now be not empty. Signed-off-by: Andrew Pinski <quic_apin...@quicinc.com>
