[Bug c++/92319] Macro expansion using the __VAOPT__ construct is incorrect when the variadic argument expands to nothing

[eldlistmailingz at tropicsoft dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92319

Edward Diener <eldlistmailingz at tropicsoft dot com> changed:

           What    |Removed                     |Added
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                 CC|                            |eldlistmailingz@tropicsoft.
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--- Comment #2 from Edward Diener <eldlistmailingz at tropicsoft dot com> ---
Created attachment 47743
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=47743&action=edit
C++ source file to illustrate bug report

Command lines on Fedora 31:

gcc.compile.c++
/home/fceldiener/build/boost/bin.v2/libs/test_local/test/test_gcc_vaopt_bug.test/gcc-c20-9.2/debug/threading-multi/visibility-hidden/test_gcc_vaopt_bug.o

    "/usr/bin/g++"   -fvisibility-inlines-hidden -fPIC -m64 -pthread -O0
-fno-inline -Wall -g -fvisibility=hidden -std=c++2a -DBOOST_ALL_NO_LIB=1 
-I"../../.." -c -o
"/home/fceldiener/build/boost/bin.v2/libs/test_local/test/test_gcc_vaopt_bug.test/gcc-c20-9.2/debug/threading-multi/visibility-hidden/test_gcc_vaopt_bug.o"
"test_gcc_vaopt_bug.cpp"

gcc.link
/home/fceldiener/build/boost/bin.v2/libs/test_local/test/test_gcc_vaopt_bug.test/gcc-c20-9.2/debug/threading-multi/visibility-hidden/test_gcc_vaopt_bug

    "/usr/bin/g++"    -o
"/home/fceldiener/build/boost/bin.v2/libs/test_local/test/test_gcc_vaopt_bug.test/gcc-c20-9.2/debug/threading-multi/visibility-hidden/test_gcc_vaopt_bug"
-Wl,--start-group
"/home/fceldiener/build/boost/bin.v2/libs/test_local/test/test_gcc_vaopt_bug.test/gcc-c20-9.2/debug/threading-multi/visibility-hidden/test_gcc_vaopt_bug.o"
 -Wl,-Bstatic  -Wl,-Bdynamic -lrt -Wl,--end-group -fPIC -m64 -pthread -g
-fvisibility=hidden -fvisibility-inlines-hidden 

Ouptut:



*********************************************************************

__cplusplus = 201709

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    Success: F()                                                               
                       f(0 )
    Failure: F(EMP)                                                            
                       f(0 , ) [expected]: f(0)


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