Fix bug that program_invocation_name is NULL when backgrounding

This is a weird issue. When elogind is started from a tty, everything
works just fine. But since adding the fixes to build elogind against
the musl libc, which does not provide program_invocation_name and
program_invocation_short_name, glibc does not set them when elogind
is background. Neither when done manually, nor when doing it using a
system init tool like openrc /sbin/start-stop-daemon.

The "workaround" is to allow elogind_set_program_name() to (re-)set
both globals if they are either NULL, or not set to the correct
value.

This should work fine with both glibc and musl-libc.

1 files changed, 13 insertions, 6 deletions

diff --git a/src/basic/musl_missing.c b/src/basic/musl_missing.c
index bdec82222..f1fbb8ca6 100644
--- a/src/basic/musl_missing.c
+++ b/src/basic/musl_missing.c
@@ -1,7 +1,7 @@
-#ifndef __GLIBC__
 #include <string.h>
 #include "util.h"
 
+#ifndef __GLIBC__
 char *program_invocation_name       = NULL;
 char *program_invocation_short_name = NULL;
 #endif // __GLIBC__
@@ -9,20 +9,27 @@ char *program_invocation_short_name = NULL;
 #include "musl_missing.h"
 
 static void elogind_free_program_name(void) {
-#ifndef __GLIBC__
         if (program_invocation_name)
                 program_invocation_name       = mfree(program_invocation_name);
         if (program_invocation_short_name)
                 program_invocation_short_name = mfree(program_invocation_short_name);
-#endif // __GLIBC__
 }
 
 void elogind_set_program_name(const char* pcall) {
         assert(pcall && pcall[0]);
-        elogind_free_program_name();
+
+        if ( ( program_invocation_name
+            && strcmp(program_invocation_name, pcall))
+          || ( program_invocation_short_name
+            && strcmp(program_invocation_short_name, basename(pcall)) ) )
+                elogind_free_program_name();
+
+        if (NULL == program_invocation_name)
+                program_invocation_name       = strdup(pcall);
+        if (NULL == program_invocation_short_name)
+                program_invocation_short_name = strdup(basename(pcall));
+
 #ifndef __GLIBC__
-        program_invocation_name       = strdup(pcall);
-        program_invocation_short_name = strdup(basename(pcall));
         atexit(elogind_free_program_name);
 #endif // __GLIBC__
 }