Apply *_FOR_BUILD flags to the native build if defined

[fabiangreffrath]

If no value is given, CMake will unset the variables just as before.

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[derselbst]

Frankly, I still don't think it's worth to incorporate such a change. Also, it doesn't work. Given the way the gentables project is currently called, no value will ever be given for any of the *_FOR_BUILD vars. So this would just always behave as complicated unset().

[helmutg]

Frankly, I still don't think it's worth to incorporate such a change. Also, it doesn't work. Given the way the gentables project is currently called, no value will ever be given for any of the *_FOR_BUILD vars. So this would just always behave as complicated unset().

It is a user (e.g. the Debian distribution) that sets *_FOR_BUILD. The origin of this PR is that Debian's QA systems verify that desired compiler flags make it into the build logs. In this instance, the flags are not strictly required, but it looks simpler to supply them than to figure out an exception rule for those invocations that don't technically need them.

And then you figured that this change does not regress anything and works as before (except when Debian uses it). Isn't that good enough then?

[derselbst]

It is a user (e.g. the Debian distribution) that sets *_FOR_BUILD

I got that, yes. But still, I don't see how this can work via ExternalProject. Have you ever tested this? If so, pls. show me how you "set" those variables so that they're actually propagated to the gentables project.

[fabiangreffrath]

They are environment variables, not CMake variables.

[derselbst]

They are environment variables, not CMake variables.

*_FOR_BUILD are CMake Variables. The following two examples should fail to compile:

cmake -DCC_FOR_BUILD=/usr/bin/false  -DCFLAGS_FOR_BUILD=gehtnich ..

export CC_FOR_BUILD=/usr/bin/false
export CFLAGS_FOR_BUILD=gehtnich
cmake ..

But they both compile fine. Why? Because you proposed a change, that doesn't work and that has presumably never been tested. Pls. come back with a proposal that actually works.

PS: I would accept one that matches up more closely with the current approach to specify a host compiler.

[fabiangreffrath]

You are right, sorry. I misquoted the variables to read them from the environment.

With the following patch it will work if the environment variables are set during the build (i.e. ninja or make) phase, not the configure (i.e. CMake) phase.

However, I understand if you don't want to hear about this topic anymore. Sorry for wasting your time. :/

--- a/src/gentables/CMakeLists.txt
+++ b/src/gentables/CMakeLists.txt
@@ -2,13 +2,13 @@ cmake_minimum_required(VERSION 3.5)
 
 # remove $CC from the current environment and by that force cmake to look for a (working) C compiler,
 # which hopefully will be the host compiler
-unset(ENV{CC})
+set(ENV{CC} $ENV{CC_FOR_BUILD})
 
 # also unset $CFLAGS to avoid passing any cross compilation flags to the host compiler
-unset(ENV{CFLAGS})
+set(ENV{CFLAGS} $ENV{CFLAGS_FOR_BUILD} $ENV{CPPFLAGS_FOR_BUILD})
 
 # linker flags as well
-unset(ENV{LDFLAGS})
+set(ENV{LDFLAGS} $ENV{LDFLAGS_FOR_BUILD})
 
 project (gentables C)