Re: completion on brace + 4 characters doesn't work

[Bart Schaefer <schaefer@xxxxxxxxxxxxxxxx>]

On Apr 29,  3:34am, Vincent Lefevre wrote:
} Subject: Re: completion on brace + 4 characters doesn't work
}
} With "echo ./{abcd", valgrind complains:
} 
} ==13848== Source and destination overlap in strcpy(0x4027532, 0x4027533)
} ==13848==    at 0x4C25918: strcpy (mc_replace_strmem.c:311)
} ==13848==    by 0xD09D92C: get_comp_string (zle_tricky.c:2016)

That's this line:

   2016                 strcpy(dbeg, dbeg + len);

The code there apparently assumes a naive implementation of strcpy()
that goes left-to-right incrementing the source and destination
pointers in lock step.  There are instances of this assumption all
over the place in get_comp_string().  It would not surprise me to
find this assumption made elsewhere in the zsh sources.

Out of curiosity, does the behavior change if you crank down the
degree of optimization (or up the of debugging) in the compiler flags
when building?

Looking at the patch below, I'm puzzled by the *dbeg = '{' assignments
-- they're to restore the string after a '\0' was plugged into it
temporarily, but isn't *dbeg immediately clobbered by whatever is
at *(dbeg+len) ?  Why bother restoring it?  I suppose len == 0 may
be possible ...

Index: Src/Zle/zle_tricky.c
===================================================================
RCS file: /extra/cvsroot/zsh/zsh-4.0/Src/Zle/zle_tricky.c,v
retrieving revision 1.30
diff -c -r1.30 zle_tricky.c
--- zle_tricky.c	21 Dec 2010 16:41:16 -0000	1.30
+++ zle_tricky.c	29 Apr 2011 03:45:13 -0000
@@ -1899,7 +1899,7 @@
 			*dbeg = '{';
 			i -= len;
 			boffs -= len;
-			strcpy(dbeg, dbeg + len);
+			memmove(dbeg, dbeg + len, 1+strlen(dbeg+len));
 			dp -= len;
 		    }
 		    bbeg = lastp = p;
@@ -1948,7 +1948,7 @@
 			*dbeg = '{';
 			i -= len;
 			boffs -= len;
-			strcpy(dbeg, dbeg + len);
+			memmove(dbeg, dbeg + len, 1+strlen(dbeg+len));
 			dp -= len;
 		    }
 		    bbeg = NULL;
@@ -2013,7 +2013,7 @@
 		new->qpos = strlen(quotename(predup, NULL));
 		*dbeg = '{';
 		boffs -= len;
-		strcpy(dbeg, dbeg + len);
+		memmove(dbeg, dbeg + len, 1+strlen(dbeg+len));
 	    }
 	    if (brend) {
 		Brinfo bp, prev = NULL;
@@ -2026,7 +2026,7 @@
 		    l = bp->qpos;
 		    bp->pos = strlen(predup + p + l);
 		    bp->qpos = strlen(quotename(predup + p + l, NULL));
-		    strcpy(predup + p, predup + p + l);
+		    memmove(predup + p, predup + p + l, 1+bp->pos);
 		}
 	    }
 	    if (hascom) {