Added support for the popular __COUNTER__ macro.

test/val/counter.c

@@ -0,0 +1,60 @@
+/* Tests for predefined macro __COUNTER__ */
+
+#include <stdio.h>
+
+static int failures = 0;
+
+#if __COUNTER__         /* 0 */
+#    error __COUNTER__ should begin at 0!
+#elif __COUNTER__ == 1  /* 1 */
+#    define CONCAT(a,b)         CONCAT_impl_(a,b)
+#    define CONCAT_impl_(a,b)   a##b
+#endif
+
+#line 42 "What is the answer?"
+int CONCAT(ident,__COUNTER__)[0+__LINE__] = {__LINE__}, CONCAT(ident,__COUNTER__)[0+__LINE__] = {__LINE__}; /* 2,3 */
+
+#if __COUNTER__ == 4 ? 1 || __COUNTER__ : 0 && __COUNTER__ /* 4,5,6 */
+_Static_assert(__COUNTER__ == 7, "__COUNTER__ should be 7 here!"); /* 7 */
+#    define GET_COUNTER()       __COUNTER__
+#    define GET_LINE()          __LINE__
+#    warning __COUNTER__ in #warning is just output as text and will never increase!
+#else
+#    if __COUNTER__ + __COUNTER__ + __COUNTER__ /* Skipped as a whole and not incrementing */
+#    endif
+#    error __COUNTER__ is skipped along with the whole #error line and will never increase anyways! */
+#endif
+
+#include "counter.h"
+#include "counter.h"
+
+_Static_assert(GET_COUNTER() == 10, "__COUNTER__ should be 10 here!"); /* 10 */
+
+int main(void)
+{
+    if (ident2[0] != 42) {
+        printf("Expected ident2[0]: %s, got: %s\n", 42, ident2[0]);
+        ++failures;
+    }
+
+    if (ident3[0] != 42) {
+        printf("Expected ident3[0]: %s, got: %s\n", 42, ident3[0]);
+        ++failures;
+    }
+
+    if (ident8 != 8) {
+        printf("Expected ident8: %s, got: %s\n", 8, ident8);
+        ++failures;
+    }
+
+    if (ident9 != 9) {
+        printf("Expected ident9: %s, got: %s\n", 9, ident9);
+        ++failures;
+    }
+
+    if (failures != 0) {
+        printf("Failures: %d\n", failures);
+    }
+
+    return failures;
+}

test/val/counter.h

@@ -0,0 +1,4 @@
+/* Tests for predefined macro __COUNTER__ */
+
+#line GET_COUNTER()  /* 1st: 8; 2nd: 9 */
+int CONCAT(ident,GET_LINE()) = GET_LINE();