#15742: GHC configure step can fail when CC=clang ----------------------------------------+--------------------------------- Reporter: judah | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Build System | Version: 8.4.3 Keywords: | Operating System: Linux Architecture: Unknown/Multiple | Type of failure: None/Unknown Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: ----------------------------------------+--------------------------------- 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 `$CC -v` and parses the output unconditionally, whether or not the compiler is actually GCC: https://github.com/ghc/ghc/blob/ce7a1c4ae4c93f2d0d3d7a0b573ddd876fc855c2/acl... In our case, the test fails since the compiler is a build of Clang that doesn't produce a useful version number. I also realized that on macOS (where gcc *is* clang), this test succeeds accidentally, since the output of {{{gcc -v}}} is: {{{ Configured with: --prefix=/Library/Developer/CommandLineTools/usr --with- gxx-include-dir=/usr/include/c++/4.2.1 Apple LLVM version 10.0.0 (clang-1000.10.44.2) Target: x86_64-apple-darwin17.7.0 Thread model: posix InstalledDir: /Library/Developer/CommandLineTools/usr/bin judahjacobson-macbookpro:~ judahjacobson$ 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/bin }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/15742 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler