oslib-posix: default exec_dir to bindir

If the exec_dir cannot be retrieved, just assume it's the installation
directory that was specified at configure time.  This makes it simpler
to reason about what the callers will do if they get back an empty
path.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

meson.build

@@ -560,7 +560,7 @@ config_host_data.set('QEMU_VERSION_MINOR', meson.project_version().split('.')[1]
 config_host_data.set('QEMU_VERSION_MICRO', meson.project_version().split('.')[2])
 
 arrays = ['CONFIG_AUDIO_DRIVERS', 'CONFIG_BDRV_RW_WHITELIST', 'CONFIG_BDRV_RO_WHITELIST']
-strings = ['HOST_DSOSUF', 'CONFIG_IASL', 'qemu_confdir', 'qemu_datadir',
+strings = ['HOST_DSOSUF', 'CONFIG_IASL', 'bindir', 'qemu_confdir', 'qemu_datadir',
            'qemu_moddir', 'qemu_localstatedir', 'qemu_helperdir', 'qemu_localedir',
            'qemu_icondir', 'qemu_desktopdir', 'qemu_firmwarepath']
 foreach k, v: config_host

util/oslib-posix.c

@@ -358,15 +358,14 @@ void qemu_set_tty_echo(int fd, bool echo)
     tcsetattr(fd, TCSANOW, &tty);
 }
 
-static char exec_dir[PATH_MAX];
+static const char *exec_dir;
 
 void qemu_init_exec_dir(const char *argv0)
 {
-    char *dir;
     char *p = NULL;
     char buf[PATH_MAX];
 
-    if (exec_dir[0]) {
+    if (exec_dir) {
         return;
     }
 
@@ -425,20 +424,14 @@ void qemu_init_exec_dir(const char *argv0)
 #endif
     /* If we don't have any way of figuring out the actual executable
        location then try argv[0].  */
-    if (!p) {
-        if (!argv0) {
-            return;
-        }
+    if (!p && argv0) {
         p = realpath(argv0, buf);
-        if (!p) {
-            return;
-        }
     }
-    dir = g_path_get_dirname(p);
-
-    pstrcpy(exec_dir, sizeof(exec_dir), dir);
-
-    g_free(dir);
+    if (p) {
+        exec_dir = g_path_get_dirname(p);
+    } else {
+        exec_dir = CONFIG_BINDIR;
+    }
 }
 
 const char *qemu_get_exec_dir(void)

util/oslib-win32.c

@@ -315,7 +315,7 @@ void qemu_set_tty_echo(int fd, bool echo)
     }
 }
 
-static char *exec_dir;
+static const char *exec_dir;
 
 void qemu_init_exec_dir(const char *argv0)
 {
@@ -341,6 +341,8 @@ void qemu_init_exec_dir(const char *argv0)
     *p = 0;
     if (access(buf, R_OK) == 0) {
         exec_dir = g_strdup(buf);
+    } else {
+        exec_dir = CONFIG_BINDIR;
     }
 }