GHC configure step can fail when CC=clang
In our internal build of GHC from source, we are building it on Linux with Clang. Unfortunately, this results in an error on ghc-8.4.3:
$ ./configure CC=clang CC_STAGE0=clang --prefix=... --with-ghc=...
...
checking version of gcc... configure: error: Need at least gcc version 4.4 (4.7+ recommended)Looking in the code, it seems that the logic is wrong: it calls $CC -v and parses the output unconditionally, whether or not the compiler is actually GCC:
https://github.com/ghc/ghc/blob/ce7a1c4ae4c93f2d0d3d7a0b573ddd876fc855c2/aclocal.m4\#L1245
In our case, the test fails since the compiler is a build of Clang that doesn't produce a useful version number.
I also realized that on macOS (where gcc *is* clang), this test succeeds accidentally, since the output of gcc -v is:
Configured with: --prefix=/Library/Developer/CommandLineTools/usr --with-gxx-include-dir=/usr/include/c++/4.2.1
Apple LLVM version 10.0.0 (clang-1000.10.44.2)
Target: x86_64-apple-darwin17.7.0
Thread model: posix
InstalledDir: /Library/Developer/CommandLineTools/usr/bin
judahjacobson-macbookpro:~ judahjacobson$ gcc -v
Configured with: --prefix=/Library/Developer/CommandLineTools/usr --with-gxx-include-dir=/usr/include/c++/4.2.1
Apple LLVM version 10.0.0 (clang-1000.10.44.2)
Target: x86_64-apple-darwin17.7.0
Thread model: posix
InstalledDir: /Library/Developer/CommandLineTools/usr/binTrac metadata
| Trac field | Value |
|---|---|
| Version | 8.4.3 |
| Type | Bug |
| TypeOfFailure | OtherFailure |
| Priority | normal |
| Resolution | Unresolved |
| Component | Build System |
| Test case | |
| Differential revisions | |
| BlockedBy | |
| Related | |
| Blocking | |
| CC | |
| Operating system | |
| Architecture |