commit 777cbe9c0faa018bafccf3e7adb8dad162276e35
Author: Érico Rolim <erico.erc@gmail.com>
Date:   Mon Feb 1 00:26:49 2021 -0300

    tests/common: fix " 37 has function" test on musl systems.
    
    This commit fixes the test that asserts on whether the lchmod() function
    should have been detected as available by Meson. It does so by assuming
    that on Linux systems not using glibc, the function will be available.
    
    - fix comment about lchmod on Linux: musl has implemented the function
    correctly since 2013, so the assumption in the test wasn't correct.
    Furthermore, musl doesn't use glibc's stub mechanism.
    - fix include to receive __GLIBC__ definition: including almost any
    header in glibc will end up defining __GLIBC__, since most headers
    include <features.h>. The <gnu/libc-version.h> header was probably
    chosen because of its name, but its actual purpose is defining functions
    for checking glibc version at runtime (instead of what the binary was
    built with), so it isn't necessary to use it. Since it is a completely
    non standard header, including it makes the test suite fail on musl due
    to not finding the header.

diff --git test cases/common/37 has function/meson.build test cases/common/37 has function/meson.build
index 26f13d6fa..a59480c2d 100644
--- a/test cases/common/39 has function/meson.build	
+++ b/test cases/common/39 has function/meson.build	
@@ -44,11 +44,13 @@ foreach cc : compilers
     error('Found non-existent function "hfkerhisadf".')
   endif
 
-  # With glibc on Linux lchmod is a stub that will always return an error,
-  # we want to detect that and declare that the function is not available.
-  # We can't check for the C library used here of course, but if it's not
-  # implemented in glibc it's probably not implemented in any other 'slimmer'
-  # C library variants either, so the check should be safe either way hopefully.
+  # With glibc (before 2.32, see below) on Linux, lchmod is a stub that will
+  # always return an error, we want to detect that and declare that the
+  # function is not available.
+  # We can't check for the C library used here of course, but the main
+  # alternative Linux C library (musl) doesn't use glibc's stub mechanism;
+  # also, it has implemented lchmod since 2013, so it should be safe to check
+  # that lchmod is available on Linux when not using glibc.
   if host_system == 'linux' or host_system == 'darwin'
     assert (cc.has_function('poll', prefix : '#include <poll.h>',
                             args : unit_test_args),
@@ -57,15 +59,24 @@ foreach cc : compilers
     has_lchmod = cc.has_function('lchmod', prefix : lchmod_prefix, args : unit_test_args)
 
     if host_system == 'linux'
-      glibc_major = cc.get_define('__GLIBC__', prefix: '#include <gnu/libc-version.h>', args: unit_test_args)
-      glibc_minor = cc.get_define('__GLIBC_MINOR__', prefix: '#include <gnu/libc-version.h>', args: unit_test_args)
-      glibc_vers = '@0@.@1@'.format(glibc_major, glibc_minor)
-      message('GLIBC vetsion:', glibc_vers)
+      # __GLIBC__ macro can be retrieved by including almost any C library header
+      glibc_major = cc.get_define('__GLIBC__', prefix: '#include <unistd.h>', args: unit_test_args)
+      # __GLIBC__ will only be set for glibc
+      if glibc_major != ''
+        glibc_print = 'hi "@0@" hi'.format(glibc_major)
+        message(glibc_print)
+        glibc_minor = cc.get_define('__GLIBC_MINOR__', prefix: '#include <unistd.h>', args: unit_test_args)
+        glibc_vers = '@0@.@1@'.format(glibc_major, glibc_minor)
+        message('GLIBC version:', glibc_vers)
 
-      # lchmod was implemented in glibc 2.32 (https://sourceware.org/pipermail/libc-announce/2020/000029.html)
-      if glibc_vers.version_compare('<2.32')
-        assert (not has_lchmod, '"lchmod" check should have failed')
+        # lchmod was implemented in glibc 2.32 (https://sourceware.org/pipermail/libc-announce/2020/000029.html)
+        if glibc_vers.version_compare('<2.32')
+          assert (not has_lchmod, '"lchmod" check should have failed')
+        else
+          assert (has_lchmod, '"lchmod" check should have succeeded')
+        endif
       else
+        # Other C libraries for Linux should have lchmod
         assert (has_lchmod, '"lchmod" check should have succeeded')
       endif
     else