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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  <jakub@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.
This commit is contained in:
Jakub Jelinek 2025-09-01 21:55:49 +02:00 committed by Jakub Jelinek
parent 086d0d8c9c
commit a4d066f364
2 changed files with 47 additions and 0 deletions
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44
gcc/testsuite/gcc.dg/cpp/c2y-counter-1.c Normal file
View File

@ -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 ();
}

3
libcpp/macro.cc
View File

@ -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: