CMake: clean up and improve build procedures

- remove check for unsupported old CMake versions

- do not link to c-ares library twice

- modernize custom Find modules

    - FindLibSSH2:
        - pass version to FPHSA to show it in the output
        - use LIBSSH2_VERSION define to extract the version number in
          one shot. This variable exists in the header for 10 years.
        - remove unneeded code

    - FindNGHTTP2.cmake:
        - drop needless FPHSA argument
        - mark found variables as advanced

    - FindNSS.cmake:
        - show version number

    - FindCARES.cmake:
        - drop default paths
        - use FPHSA instead of checking things by hand

- remove needless explict variable dereference

- simplify count_true()

- allow all policies up to version 3.16 to be set to NEW

- do not rerun check for -Wstrict-aliasing=3 every time

In contrast to every other compiler flag this has a = in it, which CMake
can't have in a variable name.

- only read the interesting strings from curlver.h

Reviewed-by: Peter Wu

Closes https://github.com/curl/curl/pull/4975

CMake/CurlSymbolHiding.cmake

@@ -11,13 +11,7 @@ if(CURL_HIDDEN_SYMBOLS)
     set(_SYMBOL_EXTERN "__attribute__ ((__visibility__ (\"default\")))")
     set(_CFLAG_SYMBOLS_HIDE "-fvisibility=hidden")
   elseif(CMAKE_COMPILER_IS_GNUCC)
-    if(NOT CMAKE_VERSION VERSION_LESS 2.8.10)
-      set(GCC_VERSION ${CMAKE_C_COMPILER_VERSION})
-    else()
-      execute_process(COMMAND ${CMAKE_C_COMPILER} -dumpversion
-                      OUTPUT_VARIABLE GCC_VERSION)
-    endif()
-    if(NOT GCC_VERSION VERSION_LESS 3.4)
+    if(NOT CMAKE_C_COMPILER_VERSION VERSION_LESS 3.4)
       # note: this is considered buggy prior to 4.0 but the autotools don't care, so let's ignore that fact
       set(SUPPORTS_SYMBOL_HIDING TRUE)
       set(_SYMBOL_EXTERN "__attribute__ ((__visibility__ (\"default\")))")

CMake/FindCARES.cmake

@@ -7,34 +7,16 @@
 # also defined, but not for general use are
 # CARES_LIBRARY, where to find the c-ares library.
 
-find_path(CARES_INCLUDE_DIR ares.h
-  /usr/local/include
-  /usr/include
-  )
+find_path(CARES_INCLUDE_DIR ares.h)
 
 set(CARES_NAMES ${CARES_NAMES} cares)
 find_library(CARES_LIBRARY
   NAMES ${CARES_NAMES}
-  PATHS /usr/lib /usr/local/lib
   )
 
-if(CARES_LIBRARY AND CARES_INCLUDE_DIR)
-  set(CARES_LIBRARIES ${CARES_LIBRARY})
-  set(CARES_FOUND "YES")
-else()
-  set(CARES_FOUND "NO")
-endif()
-
-
-if(CARES_FOUND)
-  if(NOT CARES_FIND_QUIETLY)
-    message(STATUS "Found c-ares: ${CARES_LIBRARIES}")
-  endif()
-else()
-  if(CARES_FIND_REQUIRED)
-    message(FATAL_ERROR "Could not find c-ares library")
-  endif()
-endif()
+include(FindPackageHandleStandardArgs)
+find_package_handle_standard_args(CARES
+    REQUIRED_VARS CARES_LIBRARY CARES_INCLUDE_DIR)
 
 mark_as_advanced(
   CARES_LIBRARY

CMake/FindLibSSH2.cmake

@@ -5,31 +5,18 @@
 # LIBSSH2_INCLUDE_DIR - the libssh2 include directory
 # LIBSSH2_LIBRARY - the libssh2 library name
 
-if(LIBSSH2_INCLUDE_DIR AND LIBSSH2_LIBRARY)
-  set(LibSSH2_FIND_QUIETLY TRUE)
-endif()
+find_path(LIBSSH2_INCLUDE_DIR libssh2.h)
 
-find_path(LIBSSH2_INCLUDE_DIR libssh2.h
-)
-
-find_library(LIBSSH2_LIBRARY NAMES ssh2 libssh2
-)
+find_library(LIBSSH2_LIBRARY NAMES ssh2 libssh2)
 
 if(LIBSSH2_INCLUDE_DIR)
-  file(STRINGS "${LIBSSH2_INCLUDE_DIR}/libssh2.h" libssh2_version_str REGEX "^#define[\t ]+LIBSSH2_VERSION_NUM[\t ]+0x[0-9][0-9][0-9][0-9][0-9][0-9].*")
-
-  string(REGEX REPLACE "^.*LIBSSH2_VERSION_NUM[\t ]+0x([0-9][0-9]).*$" "\\1" LIBSSH2_VERSION_MAJOR "${libssh2_version_str}")
-  string(REGEX REPLACE "^.*LIBSSH2_VERSION_NUM[\t ]+0x[0-9][0-9]([0-9][0-9]).*$" "\\1" LIBSSH2_VERSION_MINOR  "${libssh2_version_str}")
-  string(REGEX REPLACE "^.*LIBSSH2_VERSION_NUM[\t ]+0x[0-9][0-9][0-9][0-9]([0-9][0-9]).*$" "\\1" LIBSSH2_VERSION_PATCH "${libssh2_version_str}")
-
-  string(REGEX REPLACE "^0(.+)" "\\1" LIBSSH2_VERSION_MAJOR "${LIBSSH2_VERSION_MAJOR}")
-  string(REGEX REPLACE "^0(.+)" "\\1" LIBSSH2_VERSION_MINOR "${LIBSSH2_VERSION_MINOR}")
-  string(REGEX REPLACE "^0(.+)" "\\1" LIBSSH2_VERSION_PATCH "${LIBSSH2_VERSION_PATCH}")
-
-  set(LIBSSH2_VERSION "${LIBSSH2_VERSION_MAJOR}.${LIBSSH2_VERSION_MINOR}.${LIBSSH2_VERSION_PATCH}")
+  file(STRINGS "${LIBSSH2_INCLUDE_DIR}/libssh2.h" libssh2_version_str REGEX "^#define[\t ]+LIBSSH2_VERSION[\t ]+\"(.*)\"")
+  string(REGEX REPLACE "^.*\"([^\"]+)\"" "\\1"  LIBSSH2_VERSION "${libssh2_version_str}")
 endif()
 
 include(FindPackageHandleStandardArgs)
-find_package_handle_standard_args(LibSSH2 DEFAULT_MSG LIBSSH2_INCLUDE_DIR LIBSSH2_LIBRARY )
+find_package_handle_standard_args(LibSSH2
+    REQUIRED_VARS LIBSSH2_LIBRARY LIBSSH2_INCLUDE_DIR
+    VERSION_VAR LIBSSH2_VERSION)
 
-mark_as_advanced(LIBSSH2_INCLUDE_DIR LIBSSH2_LIBRARY LIBSSH2_VERSION_MAJOR LIBSSH2_VERSION_MINOR LIBSSH2_VERSION_PATCH LIBSSH2_VERSION)
+mark_as_advanced(LIBSSH2_INCLUDE_DIR LIBSSH2_LIBRARY)

CMake/FindNGHTTP2.cmake

@@ -10,9 +10,9 @@ find_package_handle_standard_args(NGHTTP2
     REQUIRED_VARS
       NGHTTP2_LIBRARY
       NGHTTP2_INCLUDE_DIR
-    FAIL_MESSAGE
-      "Could NOT find NGHTTP2"
 )
 
 set(NGHTTP2_INCLUDE_DIRS ${NGHTTP2_INCLUDE_DIR})
 set(NGHTTP2_LIBRARIES ${NGHTTP2_LIBRARY})
+
+mark_as_advanced(NGHTTP2_INCLUDE_DIRS NGHTTP2_LIBRARIES)

CMake/FindNSS.cmake

@@ -10,6 +10,8 @@ set(NSS_LIBRARIES ${PC_NSS_LINK_LIBRARIES})
 set(NSS_INCLUDE_DIRS ${PC_NSS_INCLUDE_DIRS})
 
 include(FindPackageHandleStandardArgs)
-find_package_handle_standard_args(NSS DEFAULT_MSG NSS_INCLUDE_DIRS NSS_LIBRARIES)
+find_package_handle_standard_args(NSS
+    REQUIRED_VARS NSS_LIBRARIES NSS_INCLUDE_DIRS
+    VERSION_VAR PC_NSS_VERSION)
 
 mark_as_advanced(NSS_INCLUDE_DIRS NSS_LIBRARIES)

CMake/OtherTests.cmake

@@ -32,7 +32,7 @@ int main(void) {
     return 0;
 }" curl_cv_recv)
 if(curl_cv_recv)
-  if(NOT DEFINED curl_cv_func_recv_args OR "${curl_cv_func_recv_args}" STREQUAL "unknown")
+  if(NOT DEFINED curl_cv_func_recv_args OR curl_cv_func_recv_args STREQUAL "unknown")
     foreach(recv_retv "int" "ssize_t" )
       foreach(recv_arg1 "SOCKET" "int" )
         foreach(recv_arg2 "char *" "void *" )
@@ -81,7 +81,7 @@ if(curl_cv_recv)
     string(REGEX REPLACE "^[^,]*,[^,]*,[^,]*,[^,]*,([^,]*)$" "\\1" RECV_TYPE_RETV "${curl_cv_func_recv_args}")
   endif()
 
-  if("${curl_cv_func_recv_args}" STREQUAL "unknown")
+  if(curl_cv_func_recv_args STREQUAL "unknown")
     message(FATAL_ERROR "Cannot find proper types to use for recv args")
   endif()
 else()

CMake/Utilities.cmake

@@ -2,12 +2,11 @@
 
 # Returns a list of arguments that evaluate to true
 function(count_true output_count_var)
-  set(lst)
+  set(lst_len 0)
   foreach(option_var IN LISTS ARGN)
     if(${option_var})
-      list(APPEND lst ${option_var})
+      math(EXPR lst_len "${lst_len} + 1")
     endif()
   endforeach()
-  list(LENGTH lst lst_len)
   set(${output_count_var} ${lst_len} PARENT_SCOPE)
 endfunction()