Red Hat Bugzilla – Bug 230701
Warnings issued by g++4 about broken strict-aliasing rules in /usr/include/c++/3.4.3/bits/basic_string.h when compiling with -fstrict-aliasing -Wall
Last modified: 2007-11-16 20:14:55 EST
Hi there! Description of problem: There may be some problem with the backwards compatiblity between g++-4.1 (Red Hat 4.1.0-18) and libg++ 3.4.3. When using -fstrict-aliasing optimization flag, i get warnings about broken strict-aliasing rules. The warnings do not apper when using g++ 3.4.6. Version-Release number of selected component (if applicable): Red Hat Enterprise Linux AS release 4 (Nahant Update 4) g++4 (GCC) 4.1.0 20060515 (Red Hat 4.1.0-18) How reproducible: always, just compile the following code on an x86_64 machine #include <string> int main() { std::string sausage("huhu"); } using g++4 -Wall -fstrict-aliasing -c test.cc then leave -fstrict-aliasing or use g++ should I take that warning message serious? Thank you very much! Best regards ratko
The -Wstrict-aliasing warning support was added only in 4.1+ and libstdc++-v3 4.1+ headers have been tweaked to shut the warning in this case down by additional cast through void *, but as in RHEL4 libstdc++-v3 3.4.6 is used, you get that harmless warning. The code is believed to be ok, because _S_empty_rep_storage is never written into at runtime (only initialized to 0 by the linker).