diff mbox series

c-family, c++: Reject non-string-literal error/warning attribute argument [PR126264]

Message ID CAOVfs5-okDCPb0w=7B4Ga2p4YjfS47pSkXM9Wu2EDj5RybiJ0A@mail.gmail.com
State New
Headers
Series c-family, c++: Reject non-string-literal error/warning attribute argument [PR126264] |

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Commit Message

Vladislav Semykin Aug. 5, 2026, 7:09 p.m. UTC 
  Good day!

Tools gcc-verify and gcc-style are ok. All the new tests are green.

Also, I noticed that the existing test for PR56167 needs updating:
it currently expects only a "attribute ignored" warning for both
attributes with a non-string-literal argument, whereas with this
patch that case is now a hard error. I've adjusted the expected
diagnostics accordingly.

Note that this patch only rejects non-string-literal arguments; it
does not validate the contents of a valid string literal (e.g. the
invalid escape sequence case mentioned in comment 0), which I
will be happy to edit if necessary.
diff mbox series

Patch

From 1cc1dbf933d31cbe91a534fa1cf1f8cebf0dfae6 Mon Sep 17 00:00:00 2001
From: Vladislav Semykin <vladislav.semykin@gmail.com>
Date: Wed, 5 Aug 2026 21:07:22 +0300
Subject: [PATCH v1] c-family, c++: Reject non-string-literal error/warning
 attribute argument [PR126264]
To: gcc-patches@gcc.gnu.org

	PR c++/126264
	PR c/126264

gcc/c-family/ChangeLog:

	* c-attribs.cc (handle_error_attribute): Reject a non-string-literal
	argument to the "error"/"warning" attribute with a hard error
	instead of silently ignoring it with a warning.

gcc/testsuite/ChangeLog:

	* gcc.dg/pr56167.c: Adjust expected diagnostics: a non-string-literal
	argument to "error"/"warning" on a function is now a hard error.
	* g++.dg/ext/attr-error-2.C: New test.
	* g++.dg/ext/attr-error-3.C: New test.
	* g++.dg/ext/attr-warning-2.C: New test.
	* g++.dg/ext/attr-warning-3.C: New test.
	* gcc.dg/attr-error-2.c: New test.
	* gcc.dg/attr-error-3.c: New test.
	* gcc.dg/attr-warning-2.c: New test.
	* gcc.dg/attr-warning-3.c: New test.

Signed-off-by: Vladislav Semykin <vladislav.semykin@gmail.com>
---
 gcc/c-family/c-attribs.cc                 | 14 ++++++++------
 gcc/testsuite/g++.dg/ext/attr-error-2.C   | 13 +++++++++++++
 gcc/testsuite/g++.dg/ext/attr-error-3.C   |  6 ++++++
 gcc/testsuite/g++.dg/ext/attr-warning-2.C | 13 +++++++++++++
 gcc/testsuite/g++.dg/ext/attr-warning-3.C |  6 ++++++
 gcc/testsuite/gcc.dg/attr-error-2.c       | 13 +++++++++++++
 gcc/testsuite/gcc.dg/attr-error-3.c       |  7 +++++++
 gcc/testsuite/gcc.dg/attr-warning-2.c     | 13 +++++++++++++
 gcc/testsuite/gcc.dg/attr-warning-3.c     |  7 +++++++
 gcc/testsuite/gcc.dg/pr56167.c            |  7 +++++--
 10 files changed, 91 insertions(+), 8 deletions(-)
 create mode 100644 gcc/testsuite/g++.dg/ext/attr-error-2.C
 create mode 100644 gcc/testsuite/g++.dg/ext/attr-error-3.C
 create mode 100644 gcc/testsuite/g++.dg/ext/attr-warning-2.C
 create mode 100644 gcc/testsuite/g++.dg/ext/attr-warning-3.C
 create mode 100644 gcc/testsuite/gcc.dg/attr-error-2.c
 create mode 100644 gcc/testsuite/gcc.dg/attr-error-3.c
 create mode 100644 gcc/testsuite/gcc.dg/attr-warning-2.c
 create mode 100644 gcc/testsuite/gcc.dg/attr-warning-3.c

diff --git a/gcc/c-family/c-attribs.cc b/gcc/c-family/c-attribs.cc
index d668ab96630..dbda9c67b9d 100644
--- a/gcc/c-family/c-attribs.cc
+++ b/gcc/c-family/c-attribs.cc
@@ -1925,16 +1925,18 @@  static tree
 handle_error_attribute (tree *node, tree name, tree args,
 			int ARG_UNUSED (flags), bool *no_add_attrs)
 {
-  if (TREE_CODE (*node) == FUNCTION_DECL
-      && TREE_CODE (TREE_VALUE (args)) == STRING_CST)
-    /* Do nothing else, just set the attribute.  We'll get at
-       it later with lookup_attribute.  */
-    ;
-  else
+  if (TREE_CODE (*node) != FUNCTION_DECL)
     {
       warning (OPT_Wattributes, "%qE attribute ignored", name);
       *no_add_attrs = true;
     }
+  else if (TREE_CODE (TREE_VALUE (args)) != STRING_CST)
+    {
+      error ("%qE attribute argument not a string constant", name);
+      *no_add_attrs = true;
+    }
+  /* Otherwise, do nothing else, just set the attribute.  We'll get at
+     it later with lookup_attribute.  */
 
   return NULL_TREE;
 }
diff --git a/gcc/testsuite/g++.dg/ext/attr-error-2.C b/gcc/testsuite/g++.dg/ext/attr-error-2.C
new file mode 100644
index 00000000000..47a1e95262b
--- /dev/null
+++ b/gcc/testsuite/g++.dg/ext/attr-error-2.C
@@ -0,0 +1,13 @@ 
+// PR c++/126264
+// { dg-do compile }
+
+#include <cstddef>
+
+const char * const message = "hello";
+
+void f1 () __attribute__ ((error (NULL))); // { dg-error "attribute argument not a string constant" }
+void f2 () __attribute__ ((error (0))); // { dg-error "attribute argument not a string constant" }
+void f3 () __attribute__ ((error (message))); // { dg-error "attribute argument not a string constant" }
+
+// Valid usage should still compile without diagnostics.
+void f4 () __attribute__ ((error ("f4 is deprecated"))); // { dg-bogus "attribute" }
diff --git a/gcc/testsuite/g++.dg/ext/attr-error-3.C b/gcc/testsuite/g++.dg/ext/attr-error-3.C
new file mode 100644
index 00000000000..9688717a7eb
--- /dev/null
+++ b/gcc/testsuite/g++.dg/ext/attr-error-3.C
@@ -0,0 +1,6 @@ 
+// PR c++/126264
+// nullptr is only available starting with C++11; test it separately so
+// attr-error-2.C isn't gated on a specific standard.
+// { dg-do compile { target c++11 } }
+
+void f () __attribute__ ((error (nullptr))); // { dg-error "attribute argument not a string constant" }
diff --git a/gcc/testsuite/g++.dg/ext/attr-warning-2.C b/gcc/testsuite/g++.dg/ext/attr-warning-2.C
new file mode 100644
index 00000000000..0d0c98011e9
--- /dev/null
+++ b/gcc/testsuite/g++.dg/ext/attr-warning-2.C
@@ -0,0 +1,13 @@ 
+// PR c++/126264
+// { dg-do compile }
+
+#include <cstddef>
+
+const char * const message = "hello";
+
+void f1 () __attribute__ ((warning (NULL))); // { dg-error "attribute argument not a string constant" }
+void f2 () __attribute__ ((warning (0))); // { dg-error "attribute argument not a string constant" }
+void f3 () __attribute__ ((warning (message))); // { dg-error "attribute argument not a string constant" }
+
+// Valid usage should still compile without diagnostics.
+void f4 () __attribute__ ((warning ("please avoid f4"))); // { dg-bogus "attribute" }
diff --git a/gcc/testsuite/g++.dg/ext/attr-warning-3.C b/gcc/testsuite/g++.dg/ext/attr-warning-3.C
new file mode 100644
index 00000000000..8cdf6e1a5eb
--- /dev/null
+++ b/gcc/testsuite/g++.dg/ext/attr-warning-3.C
@@ -0,0 +1,6 @@ 
+// PR c++/126264
+// nullptr is only available starting with C++11; test it separately so
+// attr-warning-2.C isn't gated on a specific standard.
+// { dg-do compile { target c++11 } }
+
+void f () __attribute__ ((warning (nullptr))); // { dg-error "attribute argument not a string constant" }
diff --git a/gcc/testsuite/gcc.dg/attr-error-2.c b/gcc/testsuite/gcc.dg/attr-error-2.c
new file mode 100644
index 00000000000..caa979d8b05
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/attr-error-2.c
@@ -0,0 +1,13 @@ 
+/* PR c/126264 */
+/* { dg-do compile } */
+
+#include <stddef.h>
+
+const char * const message = "hello";
+
+void f1 (void) __attribute__ ((error (NULL))); /* { dg-error "attribute argument not a string constant" } */
+void f2 (void) __attribute__ ((error (0))); /* { dg-error "attribute argument not a string constant" } */
+void f3 (void) __attribute__ ((error (message))); /* { dg-error "attribute argument not a string constant" } */
+
+/* Valid usage should still compile without diagnostics.  */
+void f4 (void) __attribute__ ((error ("f4 is deprecated"))); /* { dg-bogus "attribute" } */
diff --git a/gcc/testsuite/gcc.dg/attr-error-3.c b/gcc/testsuite/gcc.dg/attr-error-3.c
new file mode 100644
index 00000000000..302ce29c4f2
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/attr-error-3.c
@@ -0,0 +1,7 @@ 
+/* PR c/126264 */
+/* nullptr is only a keyword starting with C23; test it separately so
+   attr-error-2.c isn't gated on a specific standard.  */
+/* { dg-do compile } */
+/* { dg-options "-std=c23" } */
+
+void f (void) __attribute__ ((error (nullptr))); /* { dg-error "attribute argument not a string constant" } */
diff --git a/gcc/testsuite/gcc.dg/attr-warning-2.c b/gcc/testsuite/gcc.dg/attr-warning-2.c
new file mode 100644
index 00000000000..a287f9ea75c
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/attr-warning-2.c
@@ -0,0 +1,13 @@ 
+/* PR c/126264 */
+/* { dg-do compile } */
+
+#include <stddef.h>
+
+const char * const message = "hello";
+
+void f1 (void) __attribute__ ((warning (NULL))); /* { dg-error "attribute argument not a string constant" } */
+void f2 (void) __attribute__ ((warning (0))); /* { dg-error "attribute argument not a string constant" } */
+void f3 (void) __attribute__ ((warning (message))); /* { dg-error "attribute argument not a string constant" } */
+
+/* Valid usage should still compile without diagnostics.  */
+void f4 (void) __attribute__ ((warning ("please avoid f4"))); /* { dg-bogus "attribute" } */
diff --git a/gcc/testsuite/gcc.dg/attr-warning-3.c b/gcc/testsuite/gcc.dg/attr-warning-3.c
new file mode 100644
index 00000000000..c05ecb2ab21
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/attr-warning-3.c
@@ -0,0 +1,7 @@ 
+/* PR c/126264 */
+/* nullptr is only a keyword starting with C23; test it separately so
+   attr-warning-2.c isn't gated on a specific standard.  */
+/* { dg-do compile } */
+/* { dg-options "-std=c23" } */
+
+void f (void) __attribute__ ((warning (nullptr))); /* { dg-error "attribute argument not a string constant" } */
diff --git a/gcc/testsuite/gcc.dg/pr56167.c b/gcc/testsuite/gcc.dg/pr56167.c
index fc377b4756b..f0d1dcadca1 100644
--- a/gcc/testsuite/gcc.dg/pr56167.c
+++ b/gcc/testsuite/gcc.dg/pr56167.c
@@ -1,8 +1,11 @@ 
 /* PR middle-end/56167 */
+/* PR c/126264: a non-string-literal argument to the "error"/"warning"
+   attribute on a function is now a hard error rather than an ignored
+   attribute warning.  */
 /* { dg-do compile } */
 
-extern void foo (void) __attribute__ ((error (0)));	/* { dg-warning "attribute ignored" } */
-extern void bar (void) __attribute__ ((warning (0)));	/* { dg-warning "attribute ignored" } */
+extern void foo (void) __attribute__ ((error (0)));	/* { dg-error "attribute argument not a string constant" } */
+extern void bar (void) __attribute__ ((warning (0)));	/* { dg-error "attribute argument not a string constant" } */
 int var __attribute__ ((error ("foo")));		/* { dg-warning "attribute ignored" } */
 
 int

base-commit: c109d79f5bc4d4e2b65c6ee284a3d853c0173d7d
-- 
2.43.0