From: Martin Sebor <msebor@gmail.com>
To: gcc-patches <gcc-patches@gcc.gnu.org>
Subject: [PATCH] handle sanitizer built-ins in -Wuninitialized (PR 101300)
Date: Fri, 2 Jul 2021 13:21:10 -0600 [thread overview]
Message-ID: <44fabafb-9174-1739-9818-53122ef499f9@gmail.com> (raw)
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To avoid a class of false negatives for sanitized code
-Wuninitialized recognizes the ASAN_MARK internal function
doesn't modify its argument. But the warning code doesn't do
the same for any sanitizer built-ins even though they don't
modify user-supplied arguments either. This leaves another
class of false negatives unresolved.
The attached fix enhances the warning logic to recognize all
sanitizer built-ins as well and treat them as non-modifying.
Tested on x86_64-linux.
Martin
[-- Attachment #2: gcc-101300.diff --]
[-- Type: text/x-patch, Size: 2987 bytes --]
PR middle-end/101300 - -fsanitize=undefined suppresses -Wuninitialized for a VLA read at -O0
gcc/ChangeLog:
* tree-ssa-uninit.c (check_defs): Handle UBSAN built-ins.
gcc/testsuite/ChangeLog:
* gcc.dg/uninit-pr101300.c: New test.
diff --git a/gcc/tree-ssa-uninit.c b/gcc/tree-ssa-uninit.c
index 99442d7f975..dfcb7aba7c1 100644
--- a/gcc/tree-ssa-uninit.c
+++ b/gcc/tree-ssa-uninit.c
@@ -228,9 +228,26 @@ check_defs (ao_ref *ref, tree vdef, void *data_)
gimple *def_stmt = SSA_NAME_DEF_STMT (vdef);
/* The ASAN_MARK intrinsic doesn't modify the variable. */
- if (is_gimple_call (def_stmt)
- && gimple_call_internal_p (def_stmt, IFN_ASAN_MARK))
- return false;
+ if (is_gimple_call (def_stmt))
+ {
+ if (gimple_call_internal_p (def_stmt)
+ && gimple_call_internal_fn (def_stmt) == IFN_ASAN_MARK)
+ return false;
+
+ if (tree fndecl = gimple_call_fndecl (def_stmt))
+ {
+ /* Some sanitizer calls pass integer arguments to built-ins
+ that expect pointets. Avoid using gimple_call_builtin_p()
+ which fails for such calls. */
+ if (DECL_BUILT_IN_CLASS (fndecl) == BUILT_IN_NORMAL)
+ {
+ built_in_function fncode = DECL_FUNCTION_CODE (fndecl);
+ if (fncode > BEGIN_SANITIZER_BUILTINS
+ && fncode < END_SANITIZER_BUILTINS)
+ return false;
+ }
+ }
+ }
/* End of VLA scope is not a kill. */
if (gimple_call_builtin_p (def_stmt, BUILT_IN_STACK_RESTORE))
diff --git a/gcc/testsuite/gcc.dg/uninit-pr101300.c b/gcc/testsuite/gcc.dg/uninit-pr101300.c
new file mode 100644
index 00000000000..4392e8bae4f
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/uninit-pr101300.c
@@ -0,0 +1,53 @@
+/* PR middle-end/101300 - -fsanitize=undefined suppresses -Wuninitialized
+ for a VLA read at -O0
+ { dg-do compile }
+ { dg-options "-O0 -Wall -fsanitize=undefined" } */
+
+int warn_vla_rd0 (int n)
+{
+ char a[n];
+ return a[0]; // { dg-warning "\\\[-Wuninitialized]" }
+}
+
+int warn_vla_rd1 (int n)
+{
+ char a[n];
+ return a[1]; // { dg-warning "\\\[-Wuninitialized]" }
+}
+
+int warn_vla_rdi (int n, int i)
+{
+ char a[n];
+ return a[i]; // { dg-warning "\\\[-Wuninitialized]" }
+}
+
+
+int warn_vla_wr0_rd2_1_0 (int n)
+{
+ char a[n];
+ a[0] = __LINE__;
+ int x = a[2]; // { dg-warning "\\\[-Wuninitialized]" }
+ int y = a[1]; // { dg-warning "\\\[-Wuninitialized]" }
+ int z = a[0];
+ return x + y + z;
+}
+
+int warn_vla_wr1_rd2_1_0 (int n)
+{
+ char a[n];
+ a[1] = __LINE__;
+ int x = a[2]; // { dg-warning "\\\[-Wuninitialized]" }
+ int y = a[1];
+ int z = a[0]; // { dg-warning "\\\[-Wuninitialized]" }
+ return x + y + z;
+}
+
+int warn_vla_wr2_rd2_1_0 (int n)
+{
+ char a[n];
+ a[2] = __LINE__;
+ int x = a[2];
+ int y = a[1]; // { dg-warning "\\\[-Wuninitialized]" }
+ int z = a[0]; // { dg-warning "\\\[-Wuninitialized]" }
+ return x + y + z;
+}
next reply other threads:[~2021-07-02 19:21 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-02 19:21 Martin Sebor [this message]
2021-07-03 10:13 ` Bernhard Reutner-Fischer
2021-07-06 15:41 ` Martin Sebor
2021-07-12 18:06 ` PING " Martin Sebor
2021-07-20 0:01 ` PING 2 " Martin Sebor
2021-07-20 10:48 ` Jeff Law
2021-07-20 19:12 ` Martin Sebor
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