Fails to build with musl libc, undefined reference to `backtrace'

[0x6273]

Godot version

4.0 alpha 1, commit 2b61d02

System information

Gentoo, with musl libc overlay

Issue description

When linking, it does not find backtrace or backtrace_symbols. Unlike glibc, the musl libc does not come with those symbols.

From SCons output:

[100%] Linking Static Library core/libcore.linuxbsd.tools.64.a ...
Ranlib Library core/libcore.linuxbsd.tools.64.a ...
[100%] Linking Program bin/godot.linuxbsd.tools.64 ...
/usr/lib/gcc/x86_64-gentoo-linux-musl/11.2.0/../../../../x86_64-gentoo-linux-musl/bin/ld: platform/linuxbsd/crash_handler_linuxbsd.linuxbsd.tools.64.o: in function `handle_crash(int)':
/home/user/Projects/godot/platform/linuxbsd/crash_handler_linuxbsd.cpp:56: undefined reference to `backtrace'
/usr/lib/gcc/x86_64-gentoo-linux-musl/11.2.0/../../../../x86_64-gentoo-linux-musl/bin/ld: /home/user/Projects/godot/platform/linuxbsd/crash_handler_linuxbsd.cpp:80: undefined reference to `backtrace_symbols'
collect2: error: ld returned 1 exit status
scons: *** [bin/godot.linuxbsd.tools.64] Error 1
scons: building terminated because of errors.
[Time elapsed: 00:04:45.680]

Steps to reproduce

1. Have musl libc, and libexecinfo installed
2. Clone repo
3. Run scons

Minimal reproduction project

No response

[akien-mga]

Did you try build with execinfo=yes?

[0x6273]

Did you try build with execinfo=yes?

I have not tried that, but I got it to link by patching the SCsub file in platform/linuxbsd. I'm not very familiar with SCons, but would it be possible to set this automatically for systems that need execinfo?

[akien-mga]

That's already what the code does:

        BoolVariable("execinfo", "Use libexecinfo on systems where glibc is not available", False),

...

    if platform.system().find("BSD") >= 0:
        env["execinfo"] = True

    if env["execinfo"]:
        env.Append(LIBS=["execinfo"])

You just need to build with scons p=linuxbsd execinfo=yes.

I don't know if there's an easy way to detect the need for execinfo on GNU/Linux. If there's a reliable way to check from Python, this could be added to the same check that looks for *BSD.

[0x6273]

I'm not sure if there's a good way to test if libexecinfo is needed. Adding another special case for musl like we already have for BSD is probably the simplest fix.

There's a file /lib/ld-musl-$ARCH.so.1 on musl systems, so something like this would work:

if glob.glob("/lib/ld-musl-*.so*"):
    env["execinfo"] = True

[LinuxUserGD]

I'm not sure if there's a good way to test if libexecinfo is needed. Adding another special case for musl like we already have for BSD is probably the simplest fix.

There's a file /lib/ld-musl-$ARCH.so.1 on musl systems, so something like this would work:

if glob.glob("/lib/ld-musl-*.so*"):
    env["execinfo"] = True

See godotengine/godot-proposals#2439 (comment)