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authorRich Felker <dalias@aerifal.cx>2013-08-31 15:50:23 -0400
committerRich Felker <dalias@aerifal.cx>2013-08-31 15:50:23 -0400
commitdfddd43256f7ad4bad991eeff5cc51772595f327 (patch)
tree27e7540262ee86f9cdaaf283efb75230a75e3e89
parent27b4923ba00f0a7511c7ebf5f19313d6313052e9 (diff)
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debloat realpath's allocation strategy
rather than allocating a PATH_MAX-sized buffer when the caller does
not provide an output buffer, work first with a PATH_MAX-sized temp
buffer with automatic storage, and either copy it to the caller's
buffer or strdup it on success. this not only avoids massive memory
waste, but also avoids pulling in free (and thus the full malloc
implementation) unnecessarily in static programs.
-rw-r--r--src/misc/realpath.c18
1 files changed, 6 insertions, 12 deletions
diff --git a/src/misc/realpath.c b/src/misc/realpath.c
index 2b846497..43d40183 100644
--- a/src/misc/realpath.c
+++ b/src/misc/realpath.c
@@ -5,6 +5,7 @@
 #include <fcntl.h>
 #include <errno.h>
 #include <unistd.h>
+#include <string.h>
 
 void __procfdname(char *, unsigned);
 
@@ -14,7 +15,7 @@ char *realpath(const char *restrict filename, char *restrict resolved)
 	ssize_t r;
 	struct stat st1, st2;
 	char buf[15+3*sizeof(int)];
-	int alloc = 0;
+	char tmp[PATH_MAX];
 
 	if (!filename) {
 		errno = EINVAL;
@@ -25,27 +26,20 @@ char *realpath(const char *restrict filename, char *restrict resolved)
 	if (fd < 0) return 0;
 	__procfdname(buf, fd);
 
-	if (!resolved) {
-		alloc = 1;
-		resolved = malloc(PATH_MAX);
-		if (!resolved) return 0;
-	}
-
-	r = readlink(buf, resolved, PATH_MAX-1);
+	r = readlink(buf, tmp, sizeof tmp - 1);
 	if (r < 0) goto err;
-	resolved[r] = 0;
+	tmp[r] = 0;
 
 	fstat(fd, &st1);
-	r = stat(resolved, &st2);
+	r = stat(tmp, &st2);
 	if (r<0 || st1.st_dev != st2.st_dev || st1.st_ino != st2.st_ino) {
 		if (!r) errno = ELOOP;
 		goto err;
 	}
 
 	close(fd);
-	return resolved;
+	return resolved ? strcpy(resolved, tmp) : strdup(tmp);
 err:
-	if (alloc) free(resolved);
 	close(fd);
 	return 0;
 }