[lmi] gcc -fprofile-generate and -fprofile-use [Was: gcc -flto]

[Greg Chicares]

On 2016-12-24 22:41, Greg Chicares wrote:
[...]
> /opt/lmi/src/lmi[0]$make clean
> rm --force --recursive /opt/lmi/src/lmi/../build/lmi/Linux/gcc/ship
> /opt/lmi/src/lmi[0]$make debug_flag= gprof_flag="-fprofile-generate" 
> $coefficiency install check_physical_closure >../log 2>&1 
> /opt/lmi/src/lmi[0]$make system_test 
> System test:
> 
> Now I manually remove everything in the build directly except the
> 116 '.gcda' files that total 2.7 MB, and...
> 
> /opt/lmi/src/lmi[0]$time make gprof_flag="-fprofile-use" $coefficiency 
> install check_physical_closure >../log 2>&1 

With inadequate care, while battling insomnia, I repeated those steps
except that instead of manually removing everything except '*.gcda'
I did 'make clean' (removing even '*.gcda'), and then something odd
happened:

i686-w64-mingw32-g++ -MMD -MP -MT operations_posix_windows.o -MF 
operations_posix_windows.d  -c -I /opt/lmi/src/lmi -I 
/opt/lmi/src/lmi/tools/pete-2.1.1 -I 
/opt/lmi/local/lib/wx/include/i686-w64-mingw32-msw-unicode-3.1 -I 
/opt/lmi/local/include/wx-3.1 -I /opt/lmi/third_party/include -I 
/opt/lmi/third_party/src -I /opt/lmi/local/include -I 
/opt/lmi/local/include/libxml2 -DLMI_WX_NEW_USE_SO  -DLIBXML_USE_DLL -DSTRICT   
 -D_FILE_OFFSET_BITS=64 -DWXUSINGDLL -D__WXMSW__ -DBOOST_STRICT_CONFIG   
-std=c++11 -pedantic-errors -Werror -Wall -Wcast-align -Wconversion 
-Wdeprecated-declarations -Wdisabled-optimization -Wextra -Wimport -Wmultichar 
-Wpacked -Wpointer-arith -Wredundant-decls -Wsign-compare -Wundef 
-Wwrite-strings  -Wno-long-long -Wctor-dtor-privacy -Wdeprecated 
-Wnon-template-friend -Woverloaded-virtual -Wpmf-conversions -Wsynth  
-Wcast-qual  -Wno-unused-parameter -Wno-conversion -Wno-deprecated-declarations 
-Wno-parentheses -Wno-unused-local-typedefs -Wno-unused-variable     -ggdb -O2 
-fno-omit-frame-pointer -fprofile-use   
/opt/lmi/third_party/src/boost/libs/filesystem/src/operations_posix_windows.cpp 
-ooperations_posix_windows.o

/opt/lmi/third_party/src/boost/libs/filesystem/src/operations_posix_windows.cpp:
 In function 'bool boost::filesystem::equivalent(const 
boost::filesystem::path&, const boost::filesystem::path&)':
/opt/lmi/third_party/src/boost/libs/filesystem/src/operations_posix_windows.cpp:524:25:
 error: 'error1' may be used uninitialized in this function 
[-Werror=maybe-uninitialized]
           ph1, error1 ) );
                         ^
cc1plus: all warnings being treated as errors
/opt/lmi/src/lmi/workhorse.make:779: recipe for target 
'operations_posix_windows.o' failed

I think that warning is correct: if
       p1.handle != BOOST_INVALID_HANDLE_VALUE
    && p2.handle == BOOST_INVALID_HANDLE_VALUE
then 'error1' is used without ever having been initialized. But, if so,
I wonder why we've never seen that warning before: '-Wall' should enable
it, and '-Werror' should make it an error.

I won't try to figure that out, or to fix the defect. Only the text of
an exception is affected, so I'll just suppress that warning for this
file.