"_FORTIFY_SOURCE redefined" build warnings

[fwalch]

When building with manually specified _FORTIFY_SOURCE, a lot of warnings are produced during the header generation:

<command-line>:0:0: warning: "_FORTIFY_SOURCE" redefined
<command-line>:0:0: note: this is the location of the previous definition

Is there something we can do about this?

To reproduce:

rm build
make CFLAGS="-D_FORTIFY_SOURCE=2" CMAKE_BUILD_TYPE=RelWithDebInfo

[jszakmeister]

We do try: https://github.com/neovim/neovim/blob/master/CMakeLists.txt#L99

It turns out that some gcc builds (depends on the distro) set _FORTIFY_SOURCE internally, so you need to undefine it first. So if you used CFLAGS="-U_FORTIFY_SOURCE -D_FORTIFY_SOURCE=2", it might go better.

[fwalch]

Works 👍