Fix detection of backtrace() availability on FreeBSD

On FreeBSD backtrace is not part of libc and depends on libexecinfo
being available. Instead of using manual checks we can use the builtin
CMake module FindBacktrace.cmake to detect availability of backtrace()
in a portable way.

Patch By:	Alex Richardson
Differential Revision:	https://reviews.llvm.org/D27143

llvm-svn: 300062

cmake/config-ix.cmake

@@ -46,7 +46,6 @@ endfunction()
 check_include_file(dirent.h HAVE_DIRENT_H)
 check_include_file(dlfcn.h HAVE_DLFCN_H)
 check_include_file(errno.h HAVE_ERRNO_H)
-check_include_file(execinfo.h HAVE_EXECINFO_H)
 check_include_file(fcntl.h HAVE_FCNTL_H)
 check_include_file(inttypes.h HAVE_INTTYPES_H)
 check_include_file(link.h HAVE_LINK_H)
@@ -165,7 +164,9 @@ endif()
 
 # function checks
 check_symbol_exists(arc4random "stdlib.h" HAVE_DECL_ARC4RANDOM)
-check_symbol_exists(backtrace "execinfo.h" HAVE_BACKTRACE)
+find_package(Backtrace)
+set(HAVE_BACKTRACE ${Backtrace_FOUND})
+set(BACKTRACE_HEADER ${Backtrace_HEADER})
 check_symbol_exists(_Unwind_Backtrace "unwind.h" HAVE__UNWIND_BACKTRACE)
 check_symbol_exists(getpagesize unistd.h HAVE_GETPAGESIZE)
 check_symbol_exists(sysconf unistd.h HAVE_SYSCONF)

include/llvm/Config/config.h.cmake

@@ -16,6 +16,8 @@
 /* Define to 1 if you have the `backtrace' function. */
 #cmakedefine HAVE_BACKTRACE ${HAVE_BACKTRACE}
 
+#define BACKTRACE_HEADER <${BACKTRACE_HEADER}>
+
 /* Define to 1 if you have the <CrashReporterClient.h> header file. */
 #cmakedefine HAVE_CRASHREPORTERCLIENT_H
 

lib/Support/CMakeLists.txt

@@ -9,6 +9,9 @@ elseif( CMAKE_HOST_UNIX )
   if( HAVE_LIBDL )
     set(system_libs ${system_libs} ${CMAKE_DL_LIBS})
   endif()
+  if( HAVE_BACKTRACE )
+    set(system_libs ${system_libs} ${Backtrace_LIBRARIES})
+  endif()
   if(LLVM_ENABLE_TERMINFO)
     if(HAVE_TERMINFO)
       set(system_libs ${system_libs} ${TERMINFO_LIBS})
@@ -140,7 +143,7 @@ add_llvm_library(LLVMSupport
   Windows
   ${LLVM_MAIN_INCLUDE_DIR}/llvm/ADT
   ${LLVM_MAIN_INCLUDE_DIR}/llvm/Support
-
+  ${Backtrace_INCLUDE_DIRS}
   LINK_LIBS ${system_libs}
   )
 

lib/Support/Unix/Signals.inc

@@ -25,8 +25,8 @@
 #include "llvm/Support/raw_ostream.h"
 #include <algorithm>
 #include <string>
-#if HAVE_EXECINFO_H
-# include <execinfo.h>         // For backtrace().
+#ifdef HAVE_BACKTRACE
+# include BACKTRACE_HEADER         // For backtrace().
 #endif
 #if HAVE_SIGNAL_H
 #include <signal.h>