Alexander Perepelkin - 2025-10-29

Hello @dinostray,

Running the compilation with this change will cause the following warning issued for every source file when built on Ubuntu:

../include/log4cpp/threading/PThreads.hh:12: warning: "_GNU_SOURCE" redefined

And that will introduce a lot of new warnings into compilation

In details:

libtool: compile:  g++ -DHAVE_CONFIG_H -I. -I../include -I../include -Wall -Wno-unused -pedantic -MT AppenderSkeleton.lo -MD -MP -MF .deps/AppenderSkeleton.Tpo -c AppenderSkeleton.cpp  -fPIC -DPIC -o .libs/AppenderSkeleton.o
In file included from ../include/log4cpp/threading/Threading.hh:30,
                 from ../include/log4cpp/Appender.hh:25,
                 from ../include/log4cpp/AppenderSkeleton.hh:14,
                 from AppenderSkeleton.cpp:11:
../include/log4cpp/threading/PThreads.hh:12: warning: "_GNU_SOURCE" redefined
   12 | #define _GNU_SOURCE //added for cygwin compatibility
      | 
<command-line>: note: this is the location of the previous definition
libtool: compile:  g++ -DHAVE_CONFIG_H -I. -I../include -I../include -Wall -Wno-unused -pedantic -MT AppenderSkeleton.lo -MD -MP -MF .deps/AppenderSkeleton.Tpo -c AppenderSkeleton.cpp -o AppenderSkeleton.o >/dev/null 2>&1
mv -f .deps/AppenderSkeleton.Tpo .deps/AppenderSkeleton.Plo

The warnings might be worked around with fix changed to
#ifndef _GNU_SOURCE
#define _GNU_SOURCE //added for cygwin compatibility
#endif

The change is proposed a while go. Since I do not have cygwin env to try the build, I can not check whether compilation with cygwin goes well now or still not.
Could you try it out with the modern environment please (both cygwin and log4cpp)?
Perhaps there was a change since then which would make these macro unnecessary for compilation on cygwin.

Thanks