Cleaner string handling and printing of process comm

Author: nslowell

src/backtrace.c

@@ -103,15 +103,15 @@ int backtrace_snapshot(int pid, int *tids, int *index, int nr_tids)
 {
     int i, rc = 0;
     struct snapshot *snap;
-    
+
     if ((snap = get_snapshot(pid, tids, index, nr_tids)) == NULL)
         return -1;
 
     for (i = 0; i < snap->num_threads; ++i) {
-        printf("--------------------  thread %d (%d) (",
-               (index != NULL ? index[i] : i+1), snap->tids[i]);
-        print_proc_comm(snap->tids[i]);
-        printf(")  --------------------\n");
+        char comm[16];
+
+        get_thread_comm(snap->tids[i], comm, sizeof(comm));
+        printf("--------------------  thread %d (%d) (%s)  --------------------\n", (index != NULL ? index[i] : i+1), snap->tids[i], comm);
 
         snap->cur_thr = i;
         if (backtrace_thread(&snapshot_addr_space_accessors, snap) < 0)
@@ -146,11 +146,11 @@ int backtrace_ptrace(int pid, int *tids, int *index, int nr_tids)
 
     for (i = 0; i < count; ++i) {
         void *upt_info;
+        char comm[16];
+
+        get_thread_comm(threads[i], comm, sizeof(comm));
 
-        printf("--------------------  thread %d (%d) (",
-               (index != NULL ? index[i] : i+1), threads[i]);
-        print_proc_comm(threads[i]);
-        printf(")  --------------------\n");
+        printf("--------------------  thread %d (%d) (%s)  --------------------\n",(index != NULL ? index[i] : i+1), threads[i], comm);
 
         if (threads[i] != pid && attach_thread(threads[i]) < 0) {
             rc = -1;

src/proc.c

@@ -191,13 +191,18 @@ int print_proc_maps(int pid)
     return system(cmd);
 }
 
-int print_proc_comm(int pid)
+int get_thread_comm(int pid, char * dst, size_t n)
 {
     FILE *f;
-    char buf[32] = "";
-    int i;
+    char buf[32];
+    int i, x;
     int rc = -1;
 
+    if (dst == NULL)
+    {
+        return -1;
+    }
+
     snprintf(buf, sizeof(buf), "/proc/%d/comm", pid);
     if ((f = fopen(buf, "r")) == NULL) {
         fprintf(stderr, "cannot open %s: %s\n", buf, strerror(errno));
@@ -207,8 +212,10 @@ int print_proc_comm(int pid)
     if (fgets(buf, sizeof(buf), f)) {
         i = strcspn(buf, "\n");
         buf[i] = '\0';
-        printf("%s", buf);
-        rc = 0;
+        x = max(min(n-1, i+1), 0);
+        strncpy(dst, buf, x);
+        dst[x] = '\0';
+        rc = x;
     }
 
     fclose(f);

src/proc.h

@@ -28,10 +28,9 @@ struct mem_map *create_maps(int pid);
 int print_proc_maps(int pid);
 
 /*
- * simple routine to print process comm for
- * debugging or advanced error reporting
+ * copy pid process comm into dst string, up to n characters
  */
-int print_proc_comm(int pid);
+int get_thread_comm(int pid, char * dst, size_t n);
 
 /*
  * get thread identifiers of the process