Re: [hatari-devel] Crash when opening Mac preferences dialog

[Eero Tamminen <oak@xxxxxxxxxxxxxx>]

Hi Chris,

On 26.8.2023 17.33, Chris Jenkins wrote:
> I built and ran Hatari on my Mac. Hatari crashes every time I try to open
> the preferences dialog.
>
> It looks like a problem was introduced in
> commit 957d7db465970d1e34fde4c17e067c2009b32b57. Since that commit, the
> function Midi_Host_GetPortName now falls back to a prefix match on the
> supplied port name. Unfortunately, the Mac GUI code supplies a NULL pointer
> here, which causes  Midi_Host_GetPortName to blow up when it calls strlen
> on that NULL pointer.

Mac GUI code is still correct, my midi.c commit was broken.


> Attached is a patch that causes the Mac GUI to match the behaviour of the
> SDL GUI by populating the name parameter from config. This appears to fix
> the crash (the preferences dialog can open without crashing Hatari now) but
> I don't know how to test whether PortMidi actually works.

Thanks for the patch, and bisecting the issue!

However, SDL GUI gives the returned string back to 
Midi_Host_GetPortName() when using non-zero offsets.

And your patch breaks that i.e. Mac GUI would have just the name of the 
first MIDI device in the list, not all of them.


> How does the patch look? And do you have any further suggestions for
> testing this on my Mac?

Please try whether the attached patch fixes the crash.


	- Eero

From e0868746d8d11931472af6f2d6e5a6cc79699ddb Mon Sep 17 00:00:00 2001
From: Eero Tamminen <oak@xxxxxxxxxxxxxx>
Date: Sun, 27 Aug 2023 15:38:06 +0300
Subject: [PATCH] Fix Midi_Host_GetPortName() crash

Fix crash when called with NULL, and return first port name also
when called with empty string (using positive name offset).

Fixes: 957d7db465970d1e
---
 src/midi.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/src/midi.c b/src/midi.c
index 3261e8be..bf4f3607 100644
--- a/src/midi.c
+++ b/src/midi.c
@@ -429,8 +429,9 @@ static void Midi_Host_Close(void)
  *  <0: return name of device before matching one
  *  >0: return name of device after matching one
  *
- * As special case, for NULL name with positive offset,
- * name of the first port in correct direction is returned.
+ * As special case, for NULL/empty name with positive offset
+ * (i.e. before any port has been selected for the first time),
+ * name of the first port in that direction is returned.
  */
 const char* Midi_Host_GetPortName(const char *name, int offset, bool forInput)
 {
@@ -438,7 +439,9 @@ const char* Midi_Host_GetPortName(const char *name, int offset, bool forInput)
 	const char *prev = NULL;
 	const char *prefixmatch = NULL;
 	bool prev_matched = false;
-	int i, count, len = strlen(name);
+	int i, count, len;
+
+	len = name ? strlen(name) : 0;
 
 	// -- find port with given offset from named one
 	count = Pm_CountDevices();
@@ -451,7 +454,7 @@ const char* Midi_Host_GetPortName(const char *name, int offset, bool forInput)
 			continue;
 		if (!forInput && info->input)
 			continue;
-		if (!name)
+		if (len == 0)
 		{
 			if (offset <= 0)
 				return NULL;
-- 
2.39.2