cmake: replace CheckFunctionExists with CheckSymbolExists

Checking functions with `CheckFunctionExists` may
get wrong results, we should replace it with
`CheckSymbolExists`, which is recommended by the cmake
official documentation.
Before using `CheckSymbolExists`, we use
`CheckIncludeFiles` to check header files and save the
available header files in a variable that guarantees
`CheckSymbolExists` and `CheckTypeSize` to work correctly.
This approach is modeled after the cmake scripts of `curl`.

The following functions or files were not found before
modification, they can now be found:
- msys2 + mingw-8.1.0 on Windows10 or mingw-7.3.0 on Ubuntu-18.04
timerclear
timercmp
timerisset

- windows10
getaddrinfo
getnameinfo
getprotobynumber
getservbyname
putenv
strtoll
timerclear
timercmp
timerisset

- ubuntu-18.04
sys/sysctl.h
timeradd
timerclear
timercmp
timerisset

- MacOS 10.13
sys/random.h
timeradd
timerclear
timercmp
timerisset

2 files changed, 36 insertions, 20 deletions

diff --git a/cmake/CheckSymbolsExist.cmake b/cmake/CheckSymbolsExist.cmake
deleted file mode 100644
index 2c3c5dc3..00000000
--- a/cmake/CheckSymbolsExist.cmake
+++ /dev/null
@@ -1,20 +0,0 @@
-# Check if each symbol in the symbol list exists,
-# and define PREFIX__HAVE_SYMNAME to 1 if yes.
-#
-
-include(CheckSymbolExists)
-
-# SYMLIST: list of symbols to check
-# HEADERS: header files to be included in check code
-# PREFIX: the prefix of definition
-macro(CHECK_SYMBOLS_EXIST SYMLIST HEADERS PREFIX)
-  foreach(SYMNAME ${SYMLIST})
-    string(TOUPPER "${SYMNAME}" SYMNAME_UPPER)
-    if("${PREFIX}" STREQUAL "")
-      set(HAVE_SYM_DEF "HAVE_${SYMNAME_UPPER}")
-    else()
-      set(HAVE_SYM_DEF "${PREFIX}__HAVE_${SYMNAME_UPPER}")
-    endif()
-    CHECK_SYMBOL_EXISTS(${SYMNAME} "${HEADERS}" ${HAVE_SYM_DEF})
-  endforeach()
-endmacro()
diff --git a/cmake/Macros.cmake b/cmake/Macros.cmake
new file mode 100644
index 00000000..e480bbfd
--- /dev/null
+++ b/cmake/Macros.cmake
@@ -0,0 +1,36 @@
+include(CheckSymbolExists)
+include(CheckIncludeFiles)
+
+# Check if each symbol in the symbol list exists,
+# and define PREFIX__HAVE_SYMNAME to 1 if yes.
+#
+# SYMLIST: list of symbols to check
+# HEADERS: header files to be included in check code
+# PREFIX: the prefix of definition
+macro(CHECK_SYMBOLS_EXIST SYMLIST HEADERS PREFIX)
+  foreach(SYMNAME ${SYMLIST})
+    string(TOUPPER "${SYMNAME}" SYMNAME_UPPER)
+    if ("${PREFIX}" STREQUAL "")
+      set(HAVE_SYM_DEF "HAVE_${SYMNAME_UPPER}")
+    else()
+      set(HAVE_SYM_DEF "${PREFIX}__HAVE_${SYMNAME_UPPER}")
+    endif()
+    CHECK_SYMBOL_EXISTS(${SYMNAME} "${HEADERS}" ${HAVE_SYM_DEF})
+  endforeach()
+endmacro()
+
+# Check if file exists, define PREFIX__HAVE_FILE to 1 if yes,
+# and collect file to EVENT_INCLUDES
+macro(CHECK_INCLUDE_FILE_CONCAT FILE PREFIX)
+  string(REGEX REPLACE "[./]" "_" FILE_UL ${FILE})
+  string(TOUPPER "${FILE_UL}" FILE_UL_UPPER)
+  if ("${PREFIX}" STREQUAL "")
+    set(HAVE_FILE_DEF "HAVE_${FILE_UL_UPPER}")
+  else()
+    set(HAVE_FILE_DEF "${PREFIX}__HAVE_${FILE_UL_UPPER}")
+  endif()
+  CHECK_INCLUDE_FILES("${EVENT_INCLUDES};${FILE}" ${HAVE_FILE_DEF})
+  if(${HAVE_FILE_DEF})
+    set(EVENT_INCLUDES ${EVENT_INCLUDES} ${FILE})
+  endif()
+endmacro()