[PATCH] gcc-plugins/stackleak: Avoid assignment for unused macro argument

Kees Cook
2020-04-02T08:10:52Z

With GCC version >= 8, the cgraph_create_edge() macro argument using
"frequency" goes unused. Instead of assigning a temporary variable for
the argument, pass the compute_call_stmt_bb_frequency() call directly
as the macro argument so that it will just not be uncalled when it is
not wanted by the macros.

Silences the warning:

scripts/gcc-plugins/stackleak_plugin.c:54:6: warning: variable ‘frequency’ set but not used [-Wunused-but-set-variable]

Now builds cleanly with gcc-7 and gcc-9. Both boot and pass
STACKLEAK_ERASING LKDTM test.

Signed-off-by: Kees Cook <keescook@chromium.org>
---
scripts/gcc-plugins/stackleak_plugin.c | 5 ++---
1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/scripts/gcc-plugins/stackleak_plugin.c b/scripts/gcc-plugins/stackleak_plugin.c
index dbd37460c573..cc75eeba0be1 100644
--- a/scripts/gcc-plugins/stackleak_plugin.c
+++ b/scripts/gcc-plugins/stackleak_plugin.c
@@ -51,7 +51,6 @@ static void stackleak_add_track_stack(gimple_stmt_iterator *gsi, bool after)
gimple stmt;
gcall *stackleak_track_stack;
cgraph_node_ptr node;
- int frequency;
basic_block bb;

/* Insert call to void stackleak_track_stack(void) */
@@ -68,9 +67,9 @@ static void stackleak_add_track_stack(gimple_stmt_iterator *gsi, bool after)
bb = gimple_bb(stackleak_track_stack);
node = cgraph_get_create_node(track_function_decl);
gcc_assert(node);
- frequency = compute_call_stmt_bb_frequency(current_function_decl, bb);
cgraph_create_edge(cgraph_get_node(current_function_decl), node,
- stackleak_track_stack, bb->count, frequency);
+ stackleak_track_stack, bb->count,
+ compute_call_stmt_bb_frequency(current_function_decl, bb));
}

static bool is_alloca(gimple stmt)
--
2.20.1

--
Kees Cook