Prep v239: Fix an issue with program_invocation[_short]_name :

The old implementation was done assuming that only glibc provides
both program_invocation_name and program_invocation_short_name.

This worked well for users using musl-libc with the library having
been built without -D_GNU_SOURCE. However, alternative libc
implementations that actually do provide these variables, could
cause elogind to crash.

To be on the safe side, we now actually check whether both these
variables are present by letting meson check whether a code snippet
accessing these compiles and links.

2 files changed, 4 insertions, 9 deletions

diff --git a/src/shared/musl_missing.c b/src/shared/musl_missing.c
index ffa0ff78f..0f8b4d1ad 100644
--- a/src/shared/musl_missing.c
+++ b/src/shared/musl_missing.c
@@ -23,10 +23,10 @@
 
 #include "alloc-util.h"
 
-#ifndef __GLIBC__
+#if HAVE_PROGRAM_INVOCATION_NAME == 0
 char *program_invocation_name       = NULL;
 char *program_invocation_short_name = NULL;
-#endif // __GLIBC__
+#endif // libc does not provide these variables
 
 const char *program_arg_name = NULL;
 
@@ -55,8 +55,8 @@ void elogind_set_program_name(const char* pcall) {
                 program_invocation_name       = strdup(program_arg_name);
         if (NULL == program_invocation_short_name)
                 program_invocation_short_name = strdup(basename(program_arg_name));
-#ifndef __GLIBC__
+#if HAVE_PROGRAM_INVOCATION_NAME == 0
         atexit(elogind_free_program_name);
-#endif // __GLIBC__
+#endif // libc does not provide these variables
 }
 
diff --git a/src/shared/musl_missing.h b/src/shared/musl_missing.h
index 15f5f8473..cf5a01481 100644
--- a/src/shared/musl_missing.h
+++ b/src/shared/musl_missing.h
@@ -27,11 +27,6 @@ void elogind_set_program_name(const char* pcall);
 
 #define strerror_r(e, m, k) (strerror_r(e, m, k) < 0 ? strdup("strerror_r() failed") : m);
 
-#ifndef _ERRNO_H
-extern char *program_invocation_name;
-extern char *program_invocation_short_name;
-#endif // errno.h included beforehand
-
 /*
  * Possibly TODO according to http://man7.org/linux/man-pages/man3/getenv.3.html
  * + test if the process's effective user ID does not match its real user ID or