Tests do not compile with pre-release glibc

[musicinmybrain]

What is the issue you have?

In the next version of glibc, 2.34, SIGSTKSZ will be changed from a preprocessor constant to an expression involving a runtime function call. This has broken a lot of software that used it as a stack or static buffer size.

Please describe the steps to reproduce the issue.

1. Find a platform with recent enough glibc, such as Fedora 35 (Rawhide)
2. Build with CMake (or, any other approach that builds the tests).

Can you provide a small but working code example?

Not applicable.

What is the expected behavior?

Tests compile (and hopefully pass).

And what is the actual behavior instead?

[  0%] Building CXX object test/CMakeFiles/doctest_main.dir/src/unit.cpp.o
cd /builddir/build/BUILD/json-3.9.1/x86_64-redhat-linux-gnu/test && /usr/bin/g++  -I/builddir/build/BUILD/json-3.9.1/test/thirdparty/doctest -O2 -flto=auto -ffat-lto-objects -fexceptions -g -grecord-gcc-switches -pipe -Wall -Werror=format-security -Wp,-D_FORTIFY_SOURCE=2 -Wp,-D_GLIBCXX_ASSERTIONS -specs=/usr/lib/rpm/redhat/redhat-hardened-cc1 -fstack-protector-strong -specs=/usr/lib/rpm/redhat/redhat-annobin-cc1  -m64  -mtune=generic -fasynchronous-unwind-tables -fstack-clash-protection -fcf-protection -o CMakeFiles/doctest_main.dir/src/unit.cpp.o -c /builddir/build/BUILD/json-3.9.1/test/src/unit.cpp
In file included from /builddir/build/BUILD/json-3.9.1/test/thirdparty/doctest/doctest_compatibility.h:6,
                 from /builddir/build/BUILD/json-3.9.1/test/src/unit.cpp:31:
/builddir/build/BUILD/json-3.9.1/test/thirdparty/doctest/doctest.h:4021:47: error: size of array 'altStackMem' is not an integral constant-expression
 4021 |         static char             altStackMem[4 * SIGSTKSZ];
      |                                               ^

Which compiler and operating system are you using?

• Compiler: GCC 11
• Operating system: Fedora 35 (Rawhide)
• Libc: glibc 2.33.9000 (2.34 beta)

Which version of the library did you use?

• latest release version 3.9.1
• other release - please state the version: ___
• the develop branch

If you experience a compilation error: can you compile and run the unit tests?

• yes
• no - please copy/paste the error message below

See “actual behavior” above.

Additional information

This was reported upstream in doctest (doctest/doctest#473), fixed (doctest/doctest@099d541). Version 2.4.6, released three days ago, is the first to contain the fix.

This bug can be fixed by updating test/thirdparty/doctest/ to contain version 2.4.6.

[nlohmann]

Thanks for the PR! I was about to open one, but you were just too quick ;)

[xvitaly]

@nlohmann Maybe it will be better to implement building tests with packaged doctest versions and use bundled only if not found?

[nlohmann]

Maybe it will be better to implement building tests with packaged doctest versions and use bundled only if not found?

What do you mean with "packaged"?

[xvitaly]

What do you mean with "packaged"?

From distribution repositories. I can help with this.

[nlohmann]

You mean something like FetchContent?

[xvitaly]

You mean something like FetchContent?

No. Something like this:

find_package(FOO 1.0.0 QUIET)

IF (NOT FOO_FOUND)
    message(STATUS "Using bundled version of FOO library.")
    add_subdirectory("${CMAKE_SOURCE_DIR}/3rdparty/foo" EXCLUDE_FROM_ALL)
ENDIF()

[nlohmann]

I see. No, I don't think this is a good idea for this library. I only use the single header for doctest, and so far, updating was never an issue.