Add automatic configuration of compiler to get large file support (commonmark#138)

Use CheckFileOffsetBits.cmake to get correct defines for LFS. This is
necessary on 32-bit machines to avoid having trouble with file whose size
requires more than 32-bits to represent.

Signed-off-by: Keith Packard <[email protected]>

Author: keith-packard

CMakeLists.txt

@@ -9,6 +9,7 @@ endif()
 project(cmark-gfm)
 
 include("FindAsan.cmake")
+include("CheckFileOffsetBits.cmake")
 
 if("${CMAKE_SOURCE_DIR}" STREQUAL "${CMAKE_BINARY_DIR}")
     message(FATAL_ERROR "Do not build in-source.\nPlease remove CMakeCache.txt and the CMakeFiles/ directory.\nThen: mkdir build ; cd build ; cmake .. ; make")

CheckFileOffsetBits.c

@@ -0,0 +1,14 @@
+#include <sys/types.h>
+
+#define KB ((off_t)1024)
+#define MB ((off_t)1024 * KB)
+#define GB ((off_t)1024 * MB)
+#define TB ((off_t)1024 * GB)
+int t2[(((64 * GB -1) % 671088649) == 268434537)
+       && (((TB - (64 * GB -1) + 255) % 1792151290) == 305159546)? 1: -1];
+
+int main()
+{
+  ;
+  return 0;
+}

CheckFileOffsetBits.cmake

@@ -0,0 +1,43 @@
+# - Check if _FILE_OFFSET_BITS macro needed for large files
+# CHECK_FILE_OFFSET_BITS ()
+#
+# The following variables may be set before calling this macro to
+# modify the way the check is run:
+#
+#  CMAKE_REQUIRED_FLAGS = string of compile command line flags
+#  CMAKE_REQUIRED_DEFINITIONS = list of macros to define (-DFOO=bar)
+#  CMAKE_REQUIRED_INCLUDES = list of include directories
+# Copyright (c) 2009, Michihiro NAKAJIMA
+#
+# Redistribution and use is allowed according to the terms of the BSD license.
+# For details see the accompanying COPYING-CMAKE-SCRIPTS file.
+
+#INCLUDE(CheckCSourceCompiles)
+
+GET_FILENAME_COMPONENT(_selfdir_CheckFileOffsetBits
+	 "${CMAKE_CURRENT_LIST_FILE}" PATH)
+
+MACRO (CHECK_FILE_OFFSET_BITS)
+  IF(NOT DEFINED _FILE_OFFSET_BITS)
+    MESSAGE(STATUS "Checking _FILE_OFFSET_BITS for large files")
+    TRY_COMPILE(__WITHOUT_FILE_OFFSET_BITS_64
+      ${CMAKE_CURRENT_BINARY_DIR}
+      ${_selfdir_CheckFileOffsetBits}/CheckFileOffsetBits.c
+      COMPILE_DEFINITIONS ${CMAKE_REQUIRED_DEFINITIONS})
+    IF(NOT __WITHOUT_FILE_OFFSET_BITS_64)
+      TRY_COMPILE(__WITH_FILE_OFFSET_BITS_64
+        ${CMAKE_CURRENT_BINARY_DIR}
+        ${_selfdir_CheckFileOffsetBits}/CheckFileOffsetBits.c
+        COMPILE_DEFINITIONS ${CMAKE_REQUIRED_DEFINITIONS} -D_FILE_OFFSET_BITS=64)
+    ENDIF(NOT __WITHOUT_FILE_OFFSET_BITS_64)
+
+    IF(NOT __WITHOUT_FILE_OFFSET_BITS_64 AND __WITH_FILE_OFFSET_BITS_64)
+      SET(_FILE_OFFSET_BITS 64 CACHE INTERNAL "_FILE_OFFSET_BITS macro needed for large files")
+      MESSAGE(STATUS "Checking _FILE_OFFSET_BITS for large files - needed")
+    ELSE(NOT __WITHOUT_FILE_OFFSET_BITS_64 AND __WITH_FILE_OFFSET_BITS_64)
+      SET(_FILE_OFFSET_BITS "" CACHE INTERNAL "_FILE_OFFSET_BITS macro needed for large files")
+      MESSAGE(STATUS "Checking _FILE_OFFSET_BITS for large files - not needed")
+    ENDIF(NOT __WITHOUT_FILE_OFFSET_BITS_64 AND __WITH_FILE_OFFSET_BITS_64)
+  ENDIF(NOT DEFINED _FILE_OFFSET_BITS)
+
+ENDMACRO (CHECK_FILE_OFFSET_BITS)

src/CMakeLists.txt

@@ -74,6 +74,9 @@ configure_file(${CMAKE_CURRENT_SOURCE_DIR}/cmark-gfm_version.h.in
 
 include (GenerateExportHeader)
 
+include("../CheckFileOffsetBits.cmake")
+CHECK_FILE_OFFSET_BITS()
+
 add_executable(${PROGRAM} ${PROGRAM_SOURCES})
 add_compiler_export_flags()