Improve os_dlfile() interface

Might as well return the length since we have it anyway. Also this maybe
fixes the totally busted Linux code but it's still untested and probably
doesn't work for reasons that will be discovered later on.

1 files changed, 17 insertions, 9 deletions

diff --git a/src/os-unix.h b/src/os-unix.h
index 5c3c604..ec9a940 100644
--- a/src/os-unix.h
+++ b/src/os-unix.h
@@ -1,5 +1,5 @@
 /*
- * Copyright © 2022 Michael Smith <mikesmiffy128@gmail.com>
+ * Copyright © 2023 Michael Smith <mikesmiffy128@gmail.com>
  *
  * Permission to use, copy, modify, and/or distribute this software for any
  * purpose with or without fee is hereby granted, provided that the above
@@ -46,14 +46,22 @@ typedef char os_char;
 #define os_dlsym dlsym
 
 #ifdef __linux__
-static inline bool os_dlfile(void *m, char *buf, int sz) {
-	// NOTE: this might be linux/glibc-specific (I haven't checked every
-	// implementation). this is fine as we don't use it in any build-time code,
-	// only in the plugin itself. just keep it in mind!
-	struct link_map *lm = m;
-	ssz len = strlen(lm->l_name) + 1;
-	if (ssz > sz) { errno = ENAMETOOLONG; return false; }
-	memcpy(buf, lm->l_name, ssz); return true;
+// note: this is glibc-specific. it shouldn't be used in build-time code, just
+// the plugin itself (that really shouldn't be a problem).
+static inline int os_dlfile(void *m, char *buf, int sz) {
+	// private struct hidden behind _GNU_SOURCE. see dlinfo(3) or <link.h>
+	struct gnu_link_map {
+		unsigned long l_addr;
+		const char *l_name;
+		void *l_ld;
+		struct gnu_link_map *l_next, *l_prev;
+		// [more private stuff below]
+	};
+	struct gnu_link_map *lm = m;
+	int ssz = strlen(lm->l_name) + 1;
+	if (ssz > sz) { errno = ENAMETOOLONG; return -1; }
+	memcpy(buf, lm->l_name, ssz);
+	return ssz;
 }
 #endif