More reasonable fallback for self path: revisited.

This partially reverts and reworks commit
c5afb01548c5b6bf4ec83373b5e2e09f14690b01 from May 4, 2018.

I have no idea why I replaced fallback code which does
something quite reasonable: invokes realpath on the value from
argv[0]. The commit comment claims that this breaks when the
program is not invoked with an absolute path, but how can that
be, if realpath is used?

* txr.c (get_self_path): Let's keep TXR_INST_PATH, and return
that in the case that progname_u8 is null, because of a
null argv[0]. Otherwise, let's revert to the original strategy
of calling realpath on progname_u8.

1 files changed, 5 insertions, 0 deletions

diff --git a/txr.c b/txr.c
index 760b7814..43471029 100644
--- a/txr.c
+++ b/txr.c
@@ -259,6 +259,11 @@ static val get_self_path(void)
 #else
 static val get_self_path(void)
 {
+  char self[PATH_MAX];
+
+  if (progname_u8 && realpath(progname_u8, self))
+    return string_utf8(self);
+
   return lit(TXR_INST_PATH);
 }
 #endif