4486 – CodeView debug info should contain absolute path names

As of DMD 2.047, the CodeView debug information contains file names as specified on the command line, i.e. most of the time relative paths.
According to the omf-specification, the full path should be specified in the THEADR record. This makes it much easier for debuggers to find the correct source modules and can avoid ambiguities.
Here's a patch (filespec.c only contains an unusable version of making a path absolute):
Index: cgobj.c
===================================================================
--- cgobj.c	(revision 576)
+++ cgobj.c	(working copy)
@@ -17,6 +17,7 @@
 #include <stdlib.h>
 #include <malloc.h>
 #include <ctype.h>
+#include <direct.h>
 
 #include "filespec.h"
 
@@ -1249,7 +1250,20 @@
 void obj_theadr(const char *modname)
 { char *theadr;
 int i;
+ char absname[260];
 
+ if(modname[0] != '\\' && modname[0] != '/' && !(modname[0] && modname[1] == ':'))
+ {
+ if(getcwd(absname, sizeof(absname)))
+ {
+ int len = strlen(absname);
+ if(absname[len - 1] != '\\' && absname[len - 1] != '/')
+ absname[len++] = '\\';
+ strcpy(absname + len, modname);
+ modname = absname;
+ }
+ }
+
 //printf("obj_theadr(%s)\n", modname);
 theadr = (char *)alloca(ONS_OHD + strlen(modname));
 i = obj_namestring(theadr,modname);

https://github.com/D-Programming-Language/dmd/commit/a73564e2a477928694cbe88d724e8b8780040455
https://github.com/D-Programming-Language/dmd/commit/7ea404b43d928966e151d9bdce57f908a433dcb5