Add support for C99 _Bool

SWIG now treats _Bool as an alias for the bool keyword when in C mode.

CHANGES.current

@@ -7,6 +7,10 @@ the issue number to the end of the URL: https://github.com/swig/swig/issues/
 Version 4.3.0 (in progress)
 ===========================
 
+2024-09-25: olly
+	    Add support for C99 _Bool.  SWIG now treats _Bool as an alias for
+	    the bool keyword when in C mode.
+
 2024-09-24: olly
 	    #2884 SWIG no longer accepts the invalid definition of a function
 	    as the final part of a declaration, e.g.

Examples/test-suite/cbooltest.i

@@ -0,0 +1,23 @@
+%module cbooltest
+
+%{
+#if defined __STDC_VERSION__ && __STDC_VERSION__ >= 199901L
+/* C99 _Bool should be supported by the compiler. */
+# include <stdbool.h>
+#else
+/* C99 _Bool and stdbool.h may not be supported, so define a hacky version so
+ * we can still test SWIG's support. */
+# define _Bool unsigned char
+# define bool _Bool
+# define true 1
+# define false 1
+#endif
+%}
+
+%inline %{
+_Bool do_and(_Bool a, _Bool b) { return a && b; }
+_Bool do_or(_Bool a, _Bool b) { return a || b; }
+%}
+
+%constant _Bool TRUE_CONSTANT = true;
+%constant _Bool FALSE_CONSTANT = false;

Examples/test-suite/errors/cpp_c_bool.i

@@ -0,0 +1,5 @@
+%module xxx
+struct A {
+  // C99 _Bool should not be a keyword in C++ so this should not give an error.
+  bool _Bool;
+};

Examples/test-suite/php/cbooltest_runme.php

@@ -0,0 +1,8 @@
+<?php
+
+require "tests.php";
+
+check::equal(cbooltest::do_or(true, false), true, "do_or() test failed");
+check::equal(cbooltest::do_and(true, false), false, "do_and() test failed");
+check::equal(cbooltest::TRUE_CONSTANT, true, "TRUE_CONSTANT test failed");
+check::equal(cbooltest::FALSE_CONSTANT, false, "FALSE_CONSTANT test failed");

Examples/test-suite/python/cbooltest_runme.py

@@ -0,0 +1,13 @@
+import cbooltest
+
+if not cbooltest.do_or(True, False):
+    raise RuntimeError("bad _Bool support")
+
+if cbooltest.do_and(True, False):
+    raise RuntimeError("bad _Bool support")
+
+if not cbooltest.TRUE_CONSTANT:
+    raise RuntimeError("bad _Bool support")
+
+if cbooltest.FALSE_CONSTANT:
+    raise RuntimeError("bad _Bool support")

Source/CParse/cscanner.c

@@ -966,6 +966,11 @@ num_common: {
 	if (strcmp(yytext, "class") == 0) {
 	  Swig_warning(WARN_PARSE_CLASS_KEYWORD, cparse_file, cparse_line, "class keyword used, but not in C++ mode.\n");
 	}
+	if (strcmp(yytext, "_Bool") == 0) {
+	  /* C99 boolean type. */
+	  yylval.type = NewSwigType(T_BOOL);
+	  return (TYPE_BOOL);
+	}
 	if (strcmp(yytext, "_Complex") == 0) {
 	  yylval.type = NewSwigType(T_COMPLEX);
 	  return (TYPE_COMPLEX);