Format output using iovec+writev instead of malloc+copy.

1 files changed, 14 insertions, 38 deletions

diff --git a/memstomp.c b/memstomp.c
index 72817d8..b9dfafa 100644
--- a/memstomp.c
+++ b/memstomp.c
@@ -202,7 +202,9 @@ static bool verify_frame(const char *s) {
         return true;
 }
 
-static char* generate_stacktrace(void)
+#include <sys/uio.h>
+
+static void generate_stacktrace(int const fd)
 {
         void *retaddr[frames_max];  /* c99 or gcc extension */
         int const n = real_backtrace(retaddr, frames_max);
@@ -211,42 +213,18 @@ static char* generate_stacktrace(void)
         char **const strings = real_backtrace_symbols(retaddr, n);
         assert(strings);
 
-        char *ret;
-	{
-		size_t k = 0;
-		int i;
-		for (i = 0; i < n; i++)
-			k += strlen(strings[i]) + 2;
-
-		ret = malloc(k + 1);
-	}
-        assert(ret);
-
-	char *p;
+	struct iovec iov[3];
+	iov[0].iov_base = "\t";
+	iov[0].iov_len = 1;
+	iov[2].iov_base = "\n";
+	iov[2].iov_len = 1;
+	
         int i;
-	bool b = false;
-        for (i = 0, p = ret; i < n; i++) {
-                if (!b && !verify_frame(strings[i]))
-                        continue;
-
-                if (!b && i > 0) {
-                        /* Skip all but the first stack frame of ours */
-                        *(p++) = '\t';
-                        strcpy(p, strings[i-1]);
-                        p += strlen(strings[i-1]);
-                        *(p++) = '\n';
-                }
-
-                b = true;
-
-                *(p++) = '\t';
-                strcpy(p, strings[i]);
-                p += strlen(strings[i]);
-                *(p++) = '\n';
+        for (i = 0; i < n; i++) if (strings[i]) {
+		iov[1].iov_base = strings[i];
+		iov[1].iov_len = strlen(strings[i]);
+		writev(fd, iov, 3);
         }
-        *p = 0;
-        free(strings);
-        return ret;
 }
 
 int backtrace(void **array, int size)
@@ -290,9 +268,7 @@ static void warn_memcpy(void * dest, const void * src, size_t count)
  * then this is not async signal safe.  But the write() above will produce
  * some evidence before any possible trouble below.
  */
-	char *const info = generate_stacktrace();
-	fprintf(stderr, "%s", info);
-	free(info);
+	generate_stacktrace(STDERR_FILENO);
 }