remove check for __builtin_expect

Use `__has_builtin` to check at compile time if the feature is
supported. This macro is supported by both clang and GCC (as of 10).
GCC 10 was released ~2020 [1], which is ~4 years old now.  In the case
that the compiler in use is not new enough, we still provide the
fallback so that the code will compile but without the additional hints
for the branch probability (which also tends to be accounted for by
modern branch predictors).  This removes the final use of the `config.h`
header and the configure time checks.  Remove the use of `config.h` from
the code base.

[1] https://gcc.gnu.org/releases.html

src/CMakeLists.txt

@@ -169,16 +169,6 @@ if(CMARK_SHARED OR CMARK_STATIC)
 
 endif()
 
-# Feature tests
-include(CheckCSourceCompiles)
-CHECK_C_SOURCE_COMPILES(
-  "int main() { __builtin_expect(0,0); return 0; }"
-  HAVE___BUILTIN_EXPECT)
-
-CONFIGURE_FILE(
-  ${CMAKE_CURRENT_SOURCE_DIR}/config.h.in
-  ${CMAKE_CURRENT_BINARY_DIR}/config.h)
-
 if(CMARK_LIB_FUZZER)
   add_executable(cmark-fuzz ../test/cmark-fuzz.c ${LIBRARY_SOURCES})
   cmark_add_compile_options(cmark-fuzz)

src/blocks.c

@@ -12,7 +12,6 @@
 #include <stdlib.h>
 
 #include "cmark_ctype.h"
-#include "config.h"
 #include "parser.h"
 #include "cmark.h"
 #include "node.h"

src/buffer.c

@@ -7,7 +7,6 @@
 #include <stdlib.h>
 #include <string.h>
 
-#include "config.h"
 #include "cmark_ctype.h"
 #include "buffer.h"
 

src/buffer.h

@@ -1,12 +1,12 @@
 #ifndef CMARK_BUFFER_H
 #define CMARK_BUFFER_H
 
-#include <stddef.h>
-#include <stdarg.h>
-#include <string.h>
 #include <limits.h>
+#include <stdarg.h>
+#include <stddef.h>
 #include <stdint.h>
-#include "config.h"
+#include <string.h>
+
 #include "cmark.h"
 
 #ifdef __cplusplus

src/commonmark.c

@@ -5,7 +5,6 @@
 #include <stdlib.h>
 #include <string.h>
 
-#include "config.h"
 #include "cmark.h"
 #include "node.h"
 #include "buffer.h"

src/houdini.h

@@ -6,16 +6,8 @@ extern "C" {
 #endif
 
 #include <stdint.h>
-#include "config.h"
-#include "buffer.h"
 
-#ifdef HAVE___BUILTIN_EXPECT
-#define likely(x) __builtin_expect((x), 1)
-#define unlikely(x) __builtin_expect((x), 0)
-#else
-#define likely(x) (x)
-#define unlikely(x) (x)
-#endif
+#include "buffer.h"
 
 #ifdef HOUDINI_USE_LOCALE
 #define _isxdigit(c) isxdigit(c)

src/houdini_href_e.c

@@ -4,6 +4,17 @@
 
 #include "houdini.h"
 
+#if !defined(__has_builtin)
+# define __has_builtin(b) 0
+#endif
+
+#if !__has_builtin(__builtin_expect)
+# define __builtin_expect(e, v) (e)
+#endif
+
+#define likely(e) __builtin_expect((e), 1)
+#define unlikely(e) __builtin_expect((e), 0)
+
 /*
  * The following characters will not be escaped:
  *

src/houdini_html_e.c

@@ -4,6 +4,17 @@
 
 #include "houdini.h"
 
+#if !defined(__has_builtin)
+# define __has_builtin(b) 0
+#endif
+
+#if !__has_builtin(__builtin_expect)
+# define __builtin_expect(e, v) (e)
+#endif
+
+#define likely(e) __builtin_expect((e), 1)
+#define unlikely(e) __builtin_expect((e), 0)
+
 /**
  * According to the OWASP rules:
  *

src/houdini_html_u.c

@@ -7,6 +7,17 @@
 #include "utf8.h"
 #include "entities.inc"
 
+#if !defined(__has_builtin)
+# define __has_builtin(b) 0
+#endif
+
+#if !__has_builtin(__builtin_expect)
+# define __builtin_expect(e, v) (e)
+#endif
+
+#define likely(e) __builtin_expect((e), 1)
+#define unlikely(e) __builtin_expect((e), 0)
+
 /* Binary tree lookup code for entities added by JGM */
 
 static const unsigned char *S_lookup(int i, int low, int hi,

src/html.c

@@ -5,7 +5,6 @@
 #include <string.h>
 
 #include "cmark_ctype.h"
-#include "config.h"
 #include "cmark.h"
 #include "node.h"
 #include "buffer.h"

src/inlines.c

@@ -4,7 +4,6 @@
 #include <string.h>
 
 #include "cmark_ctype.h"
-#include "config.h"
 #include "node.h"
 #include "parser.h"
 #include "references.h"

src/iterator.c

@@ -2,7 +2,6 @@
 #include <stdbool.h>
 #include <stdlib.h>
 
-#include "config.h"
 #include "node.h"
 #include "cmark.h"
 #include "iterator.h"

src/latex.c

@@ -4,7 +4,6 @@
 #include <stdlib.h>
 #include <string.h>
 
-#include "config.h"
 #include "cmark.h"
 #include "node.h"
 #include "buffer.h"

src/main.c

@@ -1,8 +1,8 @@
-#include <stdlib.h>
+#include <errno.h>
 #include <stdio.h>
+#include <stdlib.h>
 #include <string.h>
-#include <errno.h>
-#include "config.h"
+
 #include "cmark.h"
 #include "node.h"
 

src/man.c

@@ -4,7 +4,6 @@
 #include <stdlib.h>
 #include <string.h>
 
-#include "config.h"
 #include "cmark.h"
 #include "node.h"
 #include "buffer.h"

src/node.c

@@ -2,7 +2,6 @@
 #include <stdlib.h>
 #include <string.h>
 
-#include "config.h"
 #include "node.h"
 
 static void S_node_unlink(cmark_node *node);

src/node.h

@@ -9,7 +9,6 @@ extern "C" {
 #include <stdint.h>
 #include <stdio.h>
 
-#include "config.h"
 #include "cmark.h"
 #include "buffer.h"
 

src/xml.c

@@ -4,7 +4,6 @@
 #include <stdlib.h>
 #include <string.h>
 
-#include "config.h"
 #include "cmark.h"
 #include "node.h"
 #include "buffer.h"