https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114525
--- Comment #6 from GCC Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Simon Martin <simar...@gcc.gnu.org>: https://gcc.gnu.org/g:35ce9afc84a63fb647a90cbecb2adf3e748178be commit r15-8911-g35ce9afc84a63fb647a90cbecb2adf3e748178be Author: Simon Martin <si...@nasilyan.com> Date: Tue Mar 25 20:11:19 2025 +0100 c++: Properly fold <COND_EXPR>.*<COMPONENT> [PR114525] We've been miscompiling the following since r0-51314-gd6b4ea8592e338 (I did not go compile something that old, and identified this change via git blame, so might be wrong) === cut here === struct Foo { int x; }; Foo& get (Foo &v) { return v; } void bar () { Foo v; v.x = 1; (true ? get (v) : get (v)).*(&Foo::x) = 2; // v.x still equals 1 here... } === cut here === The problem lies in build_m_component_ref, that computes the address of the COND_EXPR using build_address to build the representation of (true ? get (v) : get (v)).*(&Foo::x); and gets something like &(true ? get (v) : get (v)) // #1 instead of (true ? &get (v) : &get (v)) // #2 and the write does not go where want it to, hence the miscompile. This patch replaces the call to build_address by a call to cp_build_addr_expr, which gives #2, that is properly handled. PR c++/114525 gcc/cp/ChangeLog: * typeck2.cc (build_m_component_ref): Call cp_build_addr_expr instead of build_address. gcc/testsuite/ChangeLog: * g++.dg/expr/cond18.C: New test.
