Using DMD 0.121.... the following code compiles and runs fine:

# import mysql;
#
# int main()
# {
# 	MYSQL* mysql = mysql_init(null);
# 	mysql_real_connect(mysql, "localhost", "root", "", "test", 0, null, 0);
#
# 	mysql_close(mysql);
#
# 	return 0;
# }

Where mysql.d is a ported version of mysql.h.  However, if I change it to the following:

# import mysql;
#
# MYSQL* mysql;
#
# int main()
# {
# 	mysql = mysql_init(null);
# 	mysql_real_connect(mysql, "localhost", "root", "", "test", 0, null, 0);
#
# 	mysql_close(mysql);
#
# 	return 0;
# }

I get an access violation.  Commenting out the mysql_real_connect() and mysql_close() calls removes the access violation - so it's not mysql_init (which gives me the pointer.)

I thought maybe it was the garbage collector or something (note that I do not own the memory mysql points to), but even setting mysql to null before the return seems to crash.

I doubt this is a bug or anything, rather it's likely something that's not coming to mind just now.  Anyone willing to reveal my ignorance?

-[Unknown]

I've played with this a bit more, and if I do this:

# import mysql;
#
# MYSQL* mysql;
#
# int main()
# {
# 	mysql = mysql_init(null);
# 	mysql_real_connect(mysql, "localhost", "root", "", "test", 0, null, 0);
#
# 	MYSQL_RES* result = null;
# 	delete result;
#
# 	mysql_close(mysql);
#
# 	return 0;
# }

Yes, that's right, I'm deleting a null pointer.  IMHO, that should be an error.  The funny thing is... it no longer crashes like this.  If I don't delete the pointer, (even if I still declare it) it crashes.  I can also call mysql_free_result() on it, and that will also stop it from crashing.

Now I'm beginning to worry it's the GC again.  I mean, the only possible thing deleting a null pointer could do is make the garbage collector bounce around.

And, just to make things stranger: if I stick those two lines in another function, and call the function from main... it goes back to crashing. Clearly, it is my intention to be able to run queries from functions, not from the main() function only.  I should note that, as long as I do those two lines in main(), I can run queries elsewhere too.

Please forgive me for replying/talking to myself.  It's a bad habit - comes from instanity.  Sorry.

-[Unknown]

I found the problem, looking into it again today.  I was using the ported headers available from the links page.

However, these ported headers replaced "unsigned long" with "ulong", which was incorrect.  After replacing "ulong" with "uint", everything works fine.  As it turns out, I WAS writing to memory I shouldn't have been.

Allocating something extra on the stack was enough to give me something to overwrite.  Apparently, it wasn't bothering if I didn't use it; which is why I had to delete it.  In retrospect, I see I could have assigned it a dummy value too.

I'll try to send an email to the author at some point so he can correct this problem.

-[Unknown]

Unknown W. Brackets wrote:

> I found the problem, looking into it again today.  I was using the ported headers available from the links page.
> 
> However, these ported headers replaced "unsigned long" with "ulong", which was incorrect.  After replacing "ulong" with "uint", everything works fine.  As it turns out, I WAS writing to memory I shouldn't have been.
> 
> Allocating something extra on the stack was enough to give me something to overwrite.  Apparently, it wasn't bothering if I didn't use it; which is why I had to delete it.  In retrospect, I see I could have assigned it a dummy value too.
> 
> I'll try to send an email to the author at some point so he can correct this problem.
> 
> -[Unknown]

Yes please send me an email.

Manfred