I have a Flox manifest for my C/C++ development environment with
[install]
gcc.pkg-path = “gcc”
lcov.pkg-path = “lcov”
# […]
I am building test executable with coverage enabled (GCC --coverage build and link flag). However I cannot locate the gcov tool to analyze the resulting .gcda files.
After much searching, it seems the GCC NIX package hides tools like gcov?
How are people getting C/C++ code test coverage metrics using Nix GCC toolchains in a Flox environment?
Thanks.
I think using gcc-unwrapped would give you gcov.
[install]
gcc.pkg-path = “gcc-unwrapped”
lcov.pkg-path = “lcov”
# […]
The upstream nixpkgs developers actually realize this is not how it should be, but the usage of gcc and expectations are now too widespread to reverse the decision. So we just need to remember to use gcc-unwrapped (missing commands: gcov, gcc-ar, gcc-ranlib and others · Issue #86272 · NixOS/nixpkgs · GitHub).
I hope this helps.
Using gcc-unwrapped as you suggest does give me gcov
$ which gcov
<path/to>/.flox/run/x86_64-linux.edt1.dev/bin/gcov
However now the linker is missing, so it’s using my host’s linker:
$ which ld
/usr/bin/ld
Here’s a MWE:
mkdir /tmp/dummy-flox-env
cd /tmp/dummy-flox-env
flox init
flox install cmake gcc-unwrapped
Write a dummy CMakeLists.txt file to just find and test the compiler:
cmake_minimum_required(VERSION 3.16)
project(dummy
LANGUAGES C CXX
)
Then I see CMake fails to link even their simple test app to test if the compiler works. Notice it’s using the host /usr/bin/ld.
$ CC=$(which gcc) CXX=$(which g++) cmake -S . -B build
-- The C compiler identification is GNU 14.3.0
-- The CXX compiler identification is GNU 14.3.0
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - failed
-- Check for working C compiler: /tmp/dummy-flox-env/.flox/run/x86_64-linux.dummy-flox-env.dev/bin/gcc
-- Check for working C compiler: /tmp/dummy-flox-env/.flox/run/x86_64-linux.dummy-flox-env.dev/bin/gcc - broken
CMake Error at /nix/store/0vnarm4qjnj16dr3zj9kwq6bn79c0icn-cmake-3.31.7/share/cmake-3.31/Modules/CMakeTestCCompiler.cmake:67 (message):
The C compiler
"/tmp/dummy-flox-env/.flox/run/x86_64-linux.dummy-flox-env.dev/bin/gcc"
is not able to compile a simple test program.
It fails with the following output:
Change Dir: '/tmp/dummy-flox-env/build/CMakeFiles/CMakeScratch/TryCompile-hBSabD'
Run Build Command(s): /nix/store/0vnarm4qjnj16dr3zj9kwq6bn79c0icn-cmake-3.31.7/bin/cmake -E env VERBOSE=1 /usr/bin/make -f Makefile cmTC_43c1d/fast
/usr/bin/make -f CMakeFiles/cmTC_43c1d.dir/build.make CMakeFiles/cmTC_43c1d.dir/build
make[1]: Entering directory '/tmp/dummy-flox-env/build/CMakeFiles/CMakeScratch/TryCompile-hBSabD'
Building C object CMakeFiles/cmTC_43c1d.dir/testCCompiler.c.o
/tmp/dummy-flox-env/.flox/run/x86_64-linux.dummy-flox-env.dev/bin/gcc -o CMakeFiles/cmTC_43c1d.dir/testCCompiler.c.o -c /tmp/dummy-flox-env/build/CMakeFiles/CMakeScratch/TryCompile-hBSabD/testCCompiler.c
Linking C executable cmTC_43c1d
/nix/store/0vnarm4qjnj16dr3zj9kwq6bn79c0icn-cmake-3.31.7/bin/cmake -E cmake_link_script CMakeFiles/cmTC_43c1d.dir/link.txt --verbose=1
/usr/bin/ld: /nix/store/qdknxw57cwy1jkrhq7fzmiis73j42jv6-gcc-14.3.0/libexec/gcc/x86_64-unknown-linux-gnu/14.3.0/liblto_plugin.so: error loading plugin: /lib/x86_64-linux-gnu/libc.so.6: version `GLIBC_2.33' not found (required by /nix/store/qdknxw57cwy1jkrhq7fzmiis73j42jv6-gcc-14.3.0/libexec/gcc/x86_64-unknown-linux-gnu/14.3.0/liblto_plugin.so)
collect2: error: ld returned 1 exit status
/tmp/dummy-flox-env/.flox/run/x86_64-linux.dummy-flox-env.dev/bin/gcc CMakeFiles/cmTC_43c1d.dir/testCCompiler.c.o -o cmTC_43c1d
make[1]: *** [CMakeFiles/cmTC_43c1d.dir/build.make:102: cmTC_43c1d] Error 1
make[1]: Leaving directory '/tmp/dummy-flox-env/build/CMakeFiles/CMakeScratch/TryCompile-hBSabD'
make: *** [Makefile:134: cmTC_43c1d/fast] Error 2
CMake will not be able to correctly generate this project.
Call Stack (most recent call first):
CMakeLists.txt:3 (project)
-- Configuring incomplete, errors occurred!
Do you have any other ideas I can try? Thanks!