From 430a8f5e956ea8074c153c3e08e16e8e7e8e1497 Mon Sep 17 00:00:00 2001
From: Daniel Gibson <metalcaedes@gmail.com>
Date: Mon, 30 Nov 2020 02:49:27 +0100
Subject: [PATCH] POSIX: Show errormessage if loading a (Mod) .so failed, refs
 #318

.. but only if the file exists.
It's ok if mods don't have their own DLL/.so, but if they do have one
and loading fails it's interesting why they failed (e.g. no access
rights, 64bit lib with 32bit executable or other way around, missing
symbols due to wrong libc version, ...)

The same should be done for Windows, but that's still TODO.
---
 neo/sys/posix/posix_main.cpp | 23 ++++++++++++++++++++++-
 neo/sys/win32/win_main.cpp   |  3 +++
 2 files changed, 25 insertions(+), 1 deletion(-)

diff --git a/neo/sys/posix/posix_main.cpp b/neo/sys/posix/posix_main.cpp
index a060c29f..04540207 100644
--- a/neo/sys/posix/posix_main.cpp
+++ b/neo/sys/posix/posix_main.cpp
@@ -268,7 +268,28 @@ TODO: OSX - use the native API instead? NSModule
 =================
 */
 uintptr_t Sys_DLL_Load( const char *path ) {
-	return (uintptr_t)dlopen( path, RTLD_NOW );
+	void* ret = dlopen( path, RTLD_NOW );
+	if (ret == NULL) {
+		// dlopen() failed - this might be ok (we tried one possible path and the next will work)
+		// or it might be worth warning about (the lib existed but still couldn't be loaded,
+		// maybe a missing symbol or permission problems)
+		// unfortunately we only get a string from dlerror(), not some distinctive error code..
+		// so use try to open() the file to get a better idea what went wrong
+
+		int fd = open(path, O_RDONLY);
+		if (fd < 0) { // couldn't open file for reading either
+			int e = errno;
+			if(e != ENOENT) {
+				// it didn't fail because the file doesn't exist - log it, might be interesting (=> likely permission problem)
+				common->Warning("Failed to load lib '%s'! Reason: %s ( %s )\n", path, dlerror(), strerror(e));
+			}
+		} else {
+			// file could be opened, so it exists => log just dlerror()
+			close(fd);
+			common->Warning("Failed to load lib '%s' even though it exists and is readable! Reason: %s\n", path, dlerror());
+		}
+	}
+	return (uintptr_t)ret;
 }
 
 /*
diff --git a/neo/sys/win32/win_main.cpp b/neo/sys/win32/win_main.cpp
index 747b29ea..997352a6 100644
--- a/neo/sys/win32/win_main.cpp
+++ b/neo/sys/win32/win_main.cpp
@@ -600,6 +600,9 @@ uintptr_t Sys_DLL_Load( const char *dllName ) {
 			Sys_DLL_Unload( (uintptr_t)libHandle );
 			return 0;
 		}
+	} else {
+		DWORD e = GetLastError();
+		// TODO
 	}
 	return (uintptr_t)libHandle;
 }