From 4f7527f8e49276894751a9b100e68bc46568bb85 Mon Sep 17 00:00:00 2001
From: Herbert Xu <herbert@gondor.apana.org.au>
Date: Sat, 19 May 2018 02:39:48 +0800
Subject: exec: Do not allocate stack string in padvance

Many callers of padvance immediately free the allocated string
so this patch moves the stalloc call to the caller.  Instead of
returning the allocated string, padvance now returns the length
to allocate (this may be longer than the actual string length,
even including the NUL).  For the case where we would previously
return NULL, we now return -1.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
---
 src/exec.c | 26 +++++++++++++-------------
 1 file changed, 13 insertions(+), 13 deletions(-)

(limited to 'src/exec.c')

diff --git a/src/exec.c b/src/exec.c
index c98f14c..04ee2ba 100644
--- a/src/exec.c
+++ b/src/exec.c
@@ -118,13 +118,13 @@ shellexec(char **argv, const char *path, int idx)
 		e = errno;
 	} else {
 		e = ENOENT;
-		while ((cmdname = padvance(&path, argv[0])) != NULL) {
+		while (padvance(&path, argv[0]) >= 0) {
+			cmdname = stackblock();
 			if (--idx < 0 && pathopt == NULL) {
 				tryexec(cmdname, argv, envp);
 				if (errno != ENOENT && errno != ENOTDIR)
 					e = errno;
 			}
-			stunalloc(cmdname);
 		}
 	}
 
@@ -182,8 +182,7 @@ repeat:
 
 const char *pathopt;
 
-char *
-padvance(const char **path, const char *name)
+int padvance(const char **path, const char *name)
 {
 	const char *p;
 	char *q;
@@ -191,7 +190,7 @@ padvance(const char **path, const char *name)
 	size_t len;
 
 	if (*path == NULL)
-		return NULL;
+		return -1;
 	start = *path;
 	for (p = start ; *p && *p != ':' && *p != '%' ; p++);
 	len = p - start + strlen(name) + 2;	/* "2" is for '/' and '\0' */
@@ -211,7 +210,7 @@ padvance(const char **path, const char *name)
 		*path = p + 1;
 	else
 		*path = NULL;
-	return stalloc(len);
+	return len;
 }
 
 
@@ -266,9 +265,9 @@ printentry(struct tblentry *cmdp)
 	idx = cmdp->param.index;
 	path = pathval();
 	do {
-		name = padvance(&path, cmdp->cmdname);
-		stunalloc(name);
+		padvance(&path, cmdp->cmdname);
 	} while (--idx >= 0);
+	name = stackblock();
 	out1str(name);
 	out1fmt(snlfmt, cmdp->rehash ? "*" : nullstr);
 }
@@ -291,6 +290,7 @@ find_command(char *name, struct cmdentry *entry, int act, const char *path)
 	int e;
 	int updatetbl;
 	struct builtincmd *bcmd;
+	int len;
 
 	/* If name contains a slash, don't use PATH or hash table */
 	if (strchr(name, '/') != NULL) {
@@ -362,8 +362,8 @@ find_command(char *name, struct cmdentry *entry, int act, const char *path)
 	e = ENOENT;
 	idx = -1;
 loop:
-	while ((fullname = padvance(&path, name)) != NULL) {
-		stunalloc(fullname);
+	while ((len = padvance(&path, name)) >= 0) {
+		fullname = stackblock();
 		idx++;
 		if (pathopt) {
 			if (prefix(pathopt, "builtin")) {
@@ -398,7 +398,7 @@ loop:
 		if (!S_ISREG(statb.st_mode))
 			continue;
 		if (pathopt) {		/* this is a %func directory */
-			stalloc(strlen(fullname) + 1);
+			stalloc(len);
 			readcmdfile(fullname);
 			if ((cmdp = cmdlookup(name, 0)) == NULL ||
 			    cmdp->cmdtype != CMDFUNCTION)
@@ -789,9 +789,9 @@ describe_command(out, command, path, verbose)
 			p = command;
 		} else {
 			do {
-				p = padvance(&path, command);
-				stunalloc(p);
+				padvance(&path, command);
 			} while (--j >= 0);
+			p = stackblock();
 		}
 		if (verbose) {
 			outfmt(
-- 
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