[CMake] Remove HAVE_LINK_H

We can remove the variable from https://reviews.llvm.org/D5610 since
link.h is available on Linux (glibc/musl/Bionic), FreeBSD, and NetBSD.
Use `__has_include(<link.h>)` before including it.

Pull Request: #104893

Author: MaskRay

llvm/cmake/config-ix.cmake

@@ -44,7 +44,6 @@ endif()
 check_include_file(dlfcn.h HAVE_DLFCN_H)
 check_include_file(errno.h HAVE_ERRNO_H)
 check_include_file(fcntl.h HAVE_FCNTL_H)
-check_include_file(link.h HAVE_LINK_H)
 check_include_file(malloc/malloc.h HAVE_MALLOC_MALLOC_H)
 if( NOT PURE_WINDOWS )
   check_include_file(pthread.h HAVE_PTHREAD_H)

llvm/include/llvm/Config/config.h.cmake

@@ -125,9 +125,6 @@
 /* Define to 1 if you have the `pthread_setname_np' function. */
 #cmakedefine HAVE_PTHREAD_SETNAME_NP ${HAVE_PTHREAD_SETNAME_NP}
 
-/* Define to 1 if you have the <link.h> header file. */
-#cmakedefine HAVE_LINK_H ${HAVE_LINK_H}
-
 /* Define to 1 if you have the <mach/mach.h> header file. */
 #cmakedefine HAVE_MACH_MACH_H ${HAVE_MACH_MACH_H}
 

llvm/lib/Support/Unix/Signals.inc

@@ -65,7 +65,7 @@
 #ifdef __APPLE__
 #include <mach-o/dyld.h>
 #endif
-#if HAVE_LINK_H
+#if __has_include(<link.h>)
 #include <link.h>
 #endif
 #ifdef HAVE__UNWIND_BACKTRACE
@@ -464,7 +464,7 @@ void llvm::sys::AddSignalHandler(sys::SignalHandlerCallback FnPtr,
   RegisterHandlers();
 }
 
-#if ENABLE_BACKTRACES && defined(HAVE_BACKTRACE) && HAVE_LINK_H &&             \
+#if ENABLE_BACKTRACES && defined(HAVE_BACKTRACE) &&                            \
     (defined(__linux__) || defined(__FreeBSD__) ||                             \
      defined(__FreeBSD_kernel__) || defined(__NetBSD__))
 struct DlIteratePhdrData {

llvm/unittests/Support/SignalsTest.cpp

@@ -29,7 +29,7 @@ using testing::Not;
 // %i in the Symbolizer Markup Format spec
 #define I_REGEX "(0x[0-9a-fA-F]+|0[0-7]+|[0-9]+)"
 
-#if defined(HAVE_BACKTRACE) && ENABLE_BACKTRACES && HAVE_LINK_H &&             \
+#if defined(HAVE_BACKTRACE) && ENABLE_BACKTRACES &&                            \
     (defined(__linux__) || defined(__FreeBSD__) ||                             \
      defined(__FreeBSD_kernel__) || defined(__NetBSD__))
 TEST(SignalsTest, PrintsSymbolizerMarkup) {

llvm/utils/gn/secondary/llvm/include/llvm/Config/BUILD.gn

@@ -140,14 +140,12 @@ write_cmake_config("config") {
   if (current_os == "linux" || current_os == "android") {
     values += [
       "HAVE_FUTIMENS=1",
-      "HAVE_LINK_H=1",
       "HAVE_MALLINFO=1",
       "HAVE_STRUCT_STAT_ST_MTIM_TV_NSEC=1",
     ]
   } else {
     values += [
       "HAVE_FUTIMENS=",
-      "HAVE_LINK_H=",
       "HAVE_MALLINFO=",
       "HAVE_STRUCT_STAT_ST_MTIM_TV_NSEC=",
     ]

utils/bazel/llvm-project-overlay/llvm/config.bzl

@@ -47,7 +47,6 @@ posix_defines = [
 
 linux_defines = posix_defines + [
     "_GNU_SOURCE",
-    "HAVE_LINK_H=1",
     "HAVE_MALLINFO=1",
     "HAVE_SBRK=1",
     "HAVE_STRUCT_STAT_ST_MTIM_TV_NSEC=1",

utils/bazel/llvm-project-overlay/llvm/include/llvm/Config/config.h

@@ -141,9 +141,6 @@
 /* Define to 1 if you have the `pthread_setname_np' function. */
 #define HAVE_PTHREAD_SETNAME_NP 1
 
-/* Define to 1 if you have the <link.h> header file. */
-/* HAVE_LINK_H defined in Bazel */
-
 /* Define to 1 if you have the <mach/mach.h> header file. */
 /* HAVE_MACH_MACH_H defined in Bazel */
 

utils/bazel/llvm_configs/config.h.cmake

@@ -125,9 +125,6 @@
 /* Define to 1 if you have the `pthread_setname_np' function. */
 #cmakedefine HAVE_PTHREAD_SETNAME_NP ${HAVE_PTHREAD_SETNAME_NP}
 
-/* Define to 1 if you have the <link.h> header file. */
-#cmakedefine HAVE_LINK_H ${HAVE_LINK_H}
-
 /* Define to 1 if you have the <mach/mach.h> header file. */
 #cmakedefine HAVE_MACH_MACH_H ${HAVE_MACH_MACH_H}