https://gcc.gnu.org/g:a4d066f3643d3df5929425767130d68e8a775241
commit r16-3501-ga4d066f3643d3df5929425767130d68e8a775241
Author: Jakub Jelinek <ja...@redhat.com>
Date: Mon Sep 1 21:55:49 2025 +0200
c: Implement C2Y N3457 - The __COUNTER__ predefined macro
The following patch implements the
https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3457.htm
paper without the first 3 lines in Recommended practice.
Seems GCC behavior already matches the expected behavior except for
diagnostics of more than 2147483648 __COUNTER__ expansions, so the
patch adds a diagnostic for that (but not testcase because
#define A __COUNTER__ __COUNTER__ __COUNTER__ __COUNTER__ __COUNTER__
__COUNTER__ __COUNTER__ __COUNTER__
#define B A A A A A A A A
#define C B B B B B B B B
#define D C C C C C C C C
#define E D D D D D D D D
#define F E E E E E E E E
#define G F F F F F F F F
#define H G G G G G G G G
#define I H H H H H H H H
#define J I I I I I I I I
J J J J
__COUNTER__
just takes too long to preprocess).
Plus I've included all the snippets from the paper into one testcase.
2025-09-01 Jakub Jelinek <ja...@redhat.com>
* macro.cc: Implement C2Y N3457 - The __COUNTER__ predefined macro.
(_cpp_builtin_macro_text): Diagnose if __COUNTER__ reaches
2147483648 value.
* gcc.dg/cpp/c2y-counter-1.c: New test.
Diff:
---
gcc/testsuite/gcc.dg/cpp/c2y-counter-1.c | 44 ++++++++++++++++++++++++++++++++
libcpp/macro.cc | 3 +++
2 files changed, 47 insertions(+)
diff --git a/gcc/testsuite/gcc.dg/cpp/c2y-counter-1.c
b/gcc/testsuite/gcc.dg/cpp/c2y-counter-1.c
new file mode 100644
index 000000000000..47d4b236f622
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/cpp/c2y-counter-1.c
@@ -0,0 +1,44 @@
+/* N3457 - The __COUNTER__ predefined macro */
+/* { dg-do run } */
+/* { dg-options "-std=c2y -pedantic-errors" } */
+
+#ifndef __COUNTER__
+#error "__COUNTER__ not defined"
+#endif
+
+#define A(X) X + X
+static_assert (A(__COUNTER__) == 0);
+#define B(X)
+B(__COUNTER__)
+static_assert (__COUNTER__ == 1);
+#define C(...) __VA_OPT__()
+C(__COUNTER__)
+static_assert (__COUNTER__ == 3);
+#define D(...) __VA_OPT__(a)
+int D(__COUNTER__) = 1;
+static_assert (__COUNTER__ == 5);
+#define E(X) #X
+const char *b = E(__COUNTER__);
+#define F(X) a##X
+int F(__COUNTER__) = 2;
+static_assert (__COUNTER__ == 6);
+#define G(X) b##X = X
+int G(__COUNTER__);
+static_assert (__COUNTER__ == 8);
+#if !defined(__COUNTER__) || (__COUNTER__ + 1 != __COUNTER__ + 0)
+#error "Unexpected __COUNTER__ behavior")
+#endif
+static_assert (__COUNTER__ == 11);
+
+extern int strcmp (const char *, const char *);
+extern void abort ();
+
+int
+main ()
+{
+ if (a != 1
+ || strcmp (b, "__COUNTER__")
+ || a__COUNTER__ != 2
+ || b__COUNTER__ != 7)
+ abort ();
+}
diff --git a/libcpp/macro.cc b/libcpp/macro.cc
index 9867098225f7..e30760272c25 100644
--- a/libcpp/macro.cc
+++ b/libcpp/macro.cc
@@ -733,6 +733,9 @@ _cpp_builtin_macro_text (cpp_reader *pfile, cpp_hashnode
*node,
"%<__COUNTER__%> expanded inside directive with "
"%<-fdirectives-only%>");
number = pfile->counter++;
+ if (number == 0x80000000U)
+ cpp_error (pfile, CPP_DL_ERROR,
+ "%<__COUNTER__%> expanded more than 2147483648 times");
break;
case BT_HAS_ATTRIBUTE:
