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Date: Tue, 21 Sep 1999 11:03:16 +0200 (MET DST)
Message-Id: <199909210903.LAA14463@beta.informatik.hu-berlin.de>
From: Sven Wischnowsky <wischnow@informatik.hu-berlin.de>
To: zsh-workers@sunsite.auc.dk
In-reply-to: Tanaka Akira's message of 21 Sep 1999 10:38:55 +0900
Subject: Re: long string eval problem


Tanaka Akira wrote:

> Z(2):akr@localhost% Src/zsh -f
> localhost% bindkey -e; fpath=($PWD/Completion/*(/)); autoload -U compinit; compinit -D; compdef _tst tst
> localhost% _tst () { eval "$(perl -e 'print "_tst () {\n", "#" x 300000, "\n", "compadd xxx yyy\n}\n"')"; _tst "$@" }
> localhost% tst <TAB><TAB>
> 
> This causes core dump.

The problem was that the stack was filled up because `underscorelen'
never was decremented. The patch finally makes this underscore stuff
be done by a function with buffer enlargement and shrinking. Should
still be more efficient than the original always-ztrdup()
implementation.

However, the saving/restoring in runshfunc() can still cause the stack 
to fill up if we have a really large string in it and many functions
are called (nested). I don't see how we could avoid this.

Bye
 Sven

diff -u os/exec.c Src/exec.c
--- os/exec.c	Tue Sep 21 10:25:45 1999
+++ Src/exec.c	Tue Sep 21 10:57:40 1999
@@ -1413,6 +1413,27 @@
 }
 
 /**/
+void
+setunderscore(char *str)
+{
+    if (str && *str) {
+	int l = strlen(str) + 1;
+
+	if (l > underscorelen || l < (underscorelen >> 2)) {
+	    zfree(underscore, underscorelen);
+	    underscore = (char *) zalloc(underscorelen = l);
+	}
+	strcpy(underscore, str);
+	underscoreused = l;
+    } else {
+	zfree(underscore, underscorelen);
+	underscore = (char *) zalloc(underscorelen = 32);
+	*underscore = '\0';
+	underscoreused = 1;
+    }
+}
+
+/**/
 static void
 execcmd(Cmd cmd, int input, int output, int how, int last1)
 {
@@ -1629,21 +1650,8 @@
 	text = NULL;
 
     /* Set up special parameter $_ */
-    if (args && nonempty(args)) {
-	char *u = (char *) getdata(lastnode(args));
 
-	if (u) {
-	    int ul = strlen(u);
-
-	    if (ul >= underscorelen) {
-		zfree(underscore, underscorelen);
-		underscore = (char *) zalloc(underscorelen = ul + 32);
-	    }
-	    strcpy(underscore, u);
-	} else
-	    *underscore = '\0';
-    } else
-	*underscore = '\0';
+    setunderscore((args && nonempty(args)) ? ((char *) getdata(lastnode(args))) : "");
 
     /* Warn about "rm *" */
     if (type == SIMPLE && interact && unset(RMSTARSILENT)
@@ -3016,7 +3024,9 @@
 runshfunc(List list, FuncWrap wrap, char *name)
 {
     int cont;
-    VARARR(char, ou, underscorelen);
+    VARARR(char, ou, underscoreused);
+
+    memcpy(ou, underscore, underscoreused);
 
     while (wrap) {
 	wrap->module->wrapper++;
@@ -3032,9 +3042,8 @@
 	wrap = wrap->next;
     }
     startparamscope();
-    strcpy(ou, underscore);
     execlist(list, 1, 0);
-    strcpy(underscore, ou);
+    setunderscore(ou);
     endparamscope();
 }
 
@@ -3233,7 +3242,7 @@
     trapreturn = exstack->trapreturn;
     noerrs = exstack->noerrs;
     subsh_close = exstack->subsh_close;
-    strcpy(underscore, exstack->underscore);
+    setunderscore(exstack->underscore);
     zsfree(exstack->underscore);
     en = exstack->next;
     free(exstack);
diff -u os/init.c Src/init.c
--- os/init.c	Tue Sep 21 10:25:45 1999
+++ Src/init.c	Tue Sep 21 10:54:13 1999
@@ -43,7 +43,7 @@
 char *underscore;
 
 /**/
-int underscorelen;
+int underscorelen, underscoreused;
 
 /* what level of sourcing we are at */
  
@@ -625,6 +625,7 @@
     wordchars   = ztrdup(DEFAULT_WORDCHARS);
     postedit    = ztrdup("");
     underscore  = (char *) zalloc(underscorelen = 32);
+    underscoreused = 1;
     *underscore = '\0';
 
     zoptarg = ztrdup("");
diff -u os/utils.c Src/utils.c
--- os/utils.c	Tue Sep 21 10:25:47 1999
+++ Src/utils.c	Tue Sep 21 10:57:15 1999
@@ -752,14 +752,11 @@
 		    fprintf(shout, "You have new mail.\n");
 		    fflush(shout);
 		} else {
-		    VARARR(char, usav, underscorelen);
-		    int sl = strlen(*s);
+		    VARARR(char, usav, underscoreused);
 
-		    if (sl >= underscorelen) {
-			zfree(underscore, underscorelen);
-			underscore = (char *) zalloc(underscorelen = sl + 32);
-		    }
-		    strcpy(underscore, *s);
+		    memcpy(usav, underscore, underscoreused);
+
+		    setunderscore(*s);
 		    HEAPALLOC {
 			u = dupstring(u);
 			if (! parsestr(u)) {
@@ -769,7 +766,7 @@
 			    fflush(shout);
 			}
 		    } LASTALLOC;
-		    strcpy(underscore, usav);
+		    setunderscore(usav);
 		}
 	    }
 	    if (isset(MAILWARNING) && st.st_atime > st.st_mtime &&

--
Sven Wischnowsky                         wischnow@informatik.hu-berlin.de