clean up config headers

- all the compilers we support have __has_include(), so use that instead
  of checking it in cmake
- nothing in the library uses HAS__ATTRIBUTE__, so remove it

Author: QuietMisdreavus

src/CMakeLists.txt

@@ -178,14 +178,9 @@ include(CheckIncludeFile)
 include(CheckCSourceCompiles)
 include(CheckCSourceRuns)
 include(CheckSymbolExists)
-CHECK_INCLUDE_FILE(stdbool.h HAVE_STDBOOL_H)
 CHECK_C_SOURCE_COMPILES(
   "int main() { __builtin_expect(0,0); return 0; }"
   HAVE___BUILTIN_EXPECT)
-CHECK_C_SOURCE_COMPILES("
-  int f(void) __attribute__ (());
-  int main() { return 0; }
-" HAVE___ATTRIBUTE__)
 
 CONFIGURE_FILE(
   ${CMAKE_CURRENT_SOURCE_DIR}/config.h.in

src/config.h.in

@@ -5,26 +5,16 @@
 extern "C" {
 #endif
 
-#cmakedefine HAVE_STDBOOL_H
-
-#ifdef HAVE_STDBOOL_H
+#if __has_include(<stdbool.h>)
   #include <stdbool.h>
 #elif !defined(__cplusplus)
   typedef char bool;
 #endif
 
 #cmakedefine HAVE___BUILTIN_EXPECT
 
-#cmakedefine HAVE___ATTRIBUTE__
-
 #cmakedefine CMARK_THREADING
 
-#ifdef HAVE___ATTRIBUTE__
-  #define CMARK_ATTRIBUTE(list) __attribute__ (list)
-#else
-  #define CMARK_ATTRIBUTE(list)
-#endif
-
 #ifndef CMARK_INLINE
   #if defined(_MSC_VER) && !defined(__cplusplus)
     #define CMARK_INLINE __inline

src/include/cmark-gfm_config.h

@@ -9,26 +9,16 @@
 extern "C" {
 #endif
 
-#define HAVE_STDBOOL_H
-
-#ifdef HAVE_STDBOOL_H
+#if __has_include(<stdbool.h>)
   #include <stdbool.h>
 #elif !defined(__cplusplus)
   typedef char bool;
 #endif
 
 #define HAVE___BUILTIN_EXPECT
 
-#define HAVE___ATTRIBUTE__
-
 #define CMARK_THREADING
 
-#ifdef HAVE___ATTRIBUTE__
-  #define CMARK_ATTRIBUTE(list) __attribute__ (list)
-#else
-  #define CMARK_ATTRIBUTE(list)
-#endif
-
 #ifndef CMARK_INLINE
   #if defined(_MSC_VER) && !defined(__cplusplus)
     #define CMARK_INLINE __inline