The following program produces a variable scope warning, even when compiled with -ffor-scope, preventing use of -Werror. The documentation only mentions warnings being generated if the flag is not given.
int main() { int i; { for (int i = 0; i < 100; ++i); return i; } } g++ -ffor-scope -Werror -otest test.cpp cc1plus.exe: warnings being treated as errors test.cpp: In function 'int main()': test.cpp:6: warning: name lookup of 'i' changed test.cpp:3: warning: matches this 'i' under ISO standard rules test.cpp:5: warning: matches this 'i' under old rules -- Summary: For scope warning despite -ffor-scope Product: gcc Version: 4.2.1 Status: UNCONFIRMED Severity: normal Priority: P3 Component: c++ AssignedTo: unassigned at gcc dot gnu dot org ReportedBy: gcc at david dot osborn dot name GCC build triplet: i686-pc-mingw32 GCC host triplet: i686-pc-mingw32 GCC target triplet: i686-pc-mingw32 http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33260