From: Martin Uecker <uecker@tugraz.at>
Date: Fri, 26 May 2023 09:19:01 +0000 (+0200)
Subject: c: -Wstringop-overflow for parameters with forward-declared sizes
X-Git-Tag: basepoints/gcc-15~8835
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=8d6bd830f5f9c939e8565c0341a0c6c588834484;p=thirdparty%2Fgcc.git

c: -Wstringop-overflow for parameters with forward-declared sizes

Warnings from -Wstringop-overflow do not appear for parameters declared
as VLAs when the bound refers to a parameter forward declaration. This
is fixed by splitting the loop that passes through parameters into two,
first only recording the positions of all possible size expressions
and then processing the parameters.

PR c/109970

gcc/c-family:

	* c-attribs.cc (build_attr_access_from_parms): Split loop to first
	record all parameters.

gcc/testsuite:

	* gcc.dg/pr109970.c: New test.
---

diff --git a/gcc/c-family/c-attribs.cc b/gcc/c-family/c-attribs.cc
index 072cfb69147b..e2792ca6898b 100644
--- a/gcc/c-family/c-attribs.cc
+++ b/gcc/c-family/c-attribs.cc
@@ -5278,6 +5278,15 @@ build_attr_access_from_parms (tree parms, bool skip_voidptr)
       tree argtype = TREE_TYPE (arg);
       if (DECL_NAME (arg) && INTEGRAL_TYPE_P (argtype))
 	arg2pos.put (arg, argpos);
+    }
+
+  argpos = 0;
+  for (tree arg = parms; arg; arg = TREE_CHAIN (arg), ++argpos)
+    {
+      if (!DECL_P (arg))
+	continue;
+
+      tree argtype = TREE_TYPE (arg);
 
       tree argspec = DECL_ATTRIBUTES (arg);
       if (!argspec)
diff --git a/gcc/testsuite/gcc.dg/pr109970.c b/gcc/testsuite/gcc.dg/pr109970.c
new file mode 100644
index 000000000000..068c01f792dc
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr109970.c
@@ -0,0 +1,15 @@
+/* PR109970
+ * { dg-do compile }
+ * { dg-options "-Wstringop-overflow" }
+ * */
+
+void bar(int x, char buf[x]);
+void foo(int x; char buf[x], int x);
+
+int main()
+{
+	char buf[10];
+	bar(11, buf);	/* { dg-warning "accessing 11 bytes in a region of size 10" } */
+	foo(buf, 11);	/* { dg-warning "accessing 11 bytes in a region of size 10" } */
+}
+