[llvm] 48d2068 - [dsymutil] Warn on timestmap mismatch between object file and debug map

[Stephan Bergmann via llvm-commits]

On 13/01/2021 18:15, Jonas Devlieghere via llvm-commits wrote:
> 
> Author: Jonas Devlieghere
> Date: 2021-01-13T09:15:30-08:00
> New Revision: 48d2068fb738302b9fba91c9bf8e4b051c3909eb
> 
> URL: https://github.com/llvm/llvm-project/commit/48d2068fb738302b9fba91c9bf8e4b051c3909eb
> DIFF: https://github.com/llvm/llvm-project/commit/48d2068fb738302b9fba91c9bf8e4b051c3909eb.diff
> 
> LOG: [dsymutil] Warn on timestmap mismatch between object file and debug map
> 
> This re-lands e5553b9a6ab9 with two small fixes to the tests:
> 
>   - Don't touch the source directory in debug-map-parsing.test but
>     instead copy everything over in a temporary directory in
>     timestamp-mismatch.test.
>   - Don't redirect stderr to stdout to avoid the output getting
>     intertwined in extern-alias.test.

I have no idea what this warning is all about, and what exactly triggers 
it, but it looks like it breaks the

> # Check if the C compiler supports the "visibility" function attribute
> # If supported, defines HAVE_FUNC_ATTRIBUTE_VISIBILITY
> AX_GCC_FUNC_ATTRIBUTE(visibility)

configure check used by Little-CMS 
(<https://github.com/mm2/Little-CMS/blob/a0fc38ddd55a0341dafa7414ac624c1f09271401/configure.ac#L70>; 
e.g. built as part of building LibreOffice), when building on macOS:

> configure:15908: checking for __attribute__((visibility))
> configure:15930: /Users/stephan/Software/llvm/inst/bin/clang -m64 -mmacosx-version-min=10.15 -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX11.1.sdk -fno-sanitize-recover=all -ferror-limit=0 -o conftest  -ggdb2 -Xclang -debug-info-kind=constructor -O0 -fstrict-aliasing -fstrict-overflow  -I/Users/stephan/Software/lo/core/include  -I/Users/stephan/Software/adoptopenjdk.net/OpenJDK15U-jdk_x64_mac_hotspot_15.0.1_9/jdk-15.0.1+9/Contents/Home/include  -I/Users/stephan/Software/adoptopenjdk.net/OpenJDK15U-jdk_x64_mac_hotspot_15.0.1_9/jdk-15.0.1+9/Contents/Home/include/darwin  conftest.c  >&5
> warning: /Users/stephan/Software/lo/TMPDIR/conftest-01e065.o: timestamp mismatch between object file (2021-01-18 19:22:51.045749227) and debug map (2021-01-18 19:22:51.000000000)
> warning: /Users/stephan/Software/lo/TMPDIR/conftest-01e065.o: timestamp mismatch between object file (2021-01-18 19:22:51.045749227) and debug map (2021-01-18 19:22:51.000000000)
> configure:15930: $? = 0
> configure:15943: result: no

That is, the warning output apparently confuses the 
AX_GCC_FUNC_ATTRIBUTE logic and makes it erroneously assume that Clang 
does not support __attribute__((visibility)).