[PATCH dwarves 2/2] pahole: Fix -C -T segfault

[Aditya Dutt <duttaditya18@gmail.com>]

-T/--nr_definitions sets stats_formatter and sets formatter to NULL.
print_classes() checks for that before calling it.
The -C code path does not which results in a segfault.

Before:
  $ cat m.c
  struct named { int a; char b; };
  union u_named { int a; long b; };
  struct holey { char a; int b; };
  struct named s; union u_named u; struct holey h;

  $ pahole -C named -T m.o
  Segmentation fault (core dumped)

Reject the combination, similar to '-m -C'.

After:
  $ pahole -C named -T m.o
  pahole: -T/nr_definitions doesn't work with --class_name/-C, it shows all classes and the number of times they are defined
  $ echo $?
  1

  $ pahole -T m.o # unchanged
  named   1
  u_named 1
  holey   1

Fixes: f5857bd34b220a64 ("pahole: Honour --compile when -C is used")
Signed-off-by: Aditya Dutt <duttaditya18@gmail.com>
---
 pahole.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/pahole.c b/pahole.c
index aa04d98..b2047c1 100644
--- a/pahole.c
+++ b/pahole.c
@@ -3461,7 +3461,7 @@ static enum load_steal_kind pahole_stealer(struct cu *cu, struct conf_load *conf
 			print_containers(cu, class_id, 0);
 		else if (find_pointers_in_structs)
 			print_structs_with_pointer_to(cu, class_id);
-		else if (class) {
+		else if (class && formatter != NULL) {
 			/*
 			 * We don't need to print it for every compile unit
 			 * but the previous options need
@@ -3666,6 +3666,11 @@ int main(int argc, char *argv[])
 		return rc;
 	}
 
+	if (class_name != NULL && stats_formatter == nr_definitions_formatter) {
+		fputs("pahole: -T/nr_definitions doesn't work with --class_name/-C, it shows all classes and the number of times they are defined\n", stderr);
+		return rc;
+	}
+
 	if (print_numeric_version) {
 		dwarves_print_numeric_version(stdout);
 		return 0;
-- 
2.34.1