https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80633
Bug ID: 80633
Summary: [7/8 Regression] -Wstrict-aliasing false positive
Product: gcc
Version: 7.1.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: Casey at Carter dot net
Target Milestone: ---
Created attachment 41321
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=41321&action=edit
Repro (sorry, not library-free)
gcc 7.1.1 20170504 and 8.0.0 20170504 - but not 6.2/5.4/4.9.4 - incorrectly
diagnose this program:
#include <fstream>
extern void f(std::istream&);
std::ifstream ss;
using T = decltype(f(ss)); // warning: dereferencing type-punned pointer will
break strict-aliasing rules
when compiling with "gcc -Wstrict-aliasing -O2 -c". The diagnostic is notably
not emitted for "decltype(f(std::declval<std::ifstream&>()))".
