gdb/nat/linux-osdata.c: fix build on gcc-12 (string overfow)

On gcc-12 build fails as:

    ../../gdbserver/../gdb/nat/linux-osdata.c: In function 'void linux_xfer_osdata_processes(buffer*)':
    ../../gdbserver/../gdb/nat/linux-osdata.c:330:39: error:
      '__builtin___sprintf_chk' may write a terminating nul past the end of the destination [-Werror=format-overflow=]
      330 |                 sprintf (core_str, "%d", i);
          |                                       ^

It's an off-by-one case in an infeasible scenario for negative
huge core count. The change switches to std::string for memory
handling.

Tested by running 'info os processes' and checking CPU cores column.

diff --git a/gdb/nat/linux-osdata.c b/gdb/nat/linux-osdata.c
index 9746d1210fe465aa94b9f7275ae447f6d68f1527..91bbe10e515499dd191f1629fb7dd65c32bd4927 100644 (file)
--- a/gdb/nat/linux-osdata.c
+++ b/gdb/nat/linux-osdata.c
@@ -302,7 +302,7 @@ linux_xfer_osdata_processes (struct buffer *buffer)
          char *command_line;
          int *cores;
          int task_count;
-         char *cores_str;
+         std::string cores_str;
          int i;
 
          if (!isdigit (dp->d_name[0])
@@ -320,19 +320,15 @@ linux_xfer_osdata_processes (struct buffer *buffer)
          /* Find CPU cores used by the process.  */
          cores = XCNEWVEC (int, num_cores);
          task_count = get_cores_used_by_process (pid, cores, num_cores);
-         cores_str = (char *) xcalloc (task_count, sizeof ("4294967295") + 1);
 
          for (i = 0; i < num_cores && task_count > 0; ++i)
            if (cores[i])
              {
-               char core_str[sizeof ("4294967295")];
-
-               sprintf (core_str, "%d", i);
-               strcat (cores_str, core_str);
+               string_appendf (cores_str, "%d", i);
 
                task_count -= cores[i];
                if (task_count > 0)
-                 strcat (cores_str, ",");
+                 cores_str += ",";
              }
 
          xfree (cores);
@@ -348,10 +344,9 @@ linux_xfer_osdata_processes (struct buffer *buffer)
             pid,
             user,
             command_line ? command_line : "",
-            cores_str);
+            cores_str.c_str());
 
          xfree (command_line);
-         xfree (cores_str);
        }
 
       closedir (dirp);