cmake: add Findfmt.cmake

the cmake config provided by fmt-devel-3.0.2 does not offer fmt::fmt target,
so we need to offer a Findfmt.cmake to do this.

Signed-off-by: Kefu Chai <kchai@redhat.com>

cmake/modules/Findfmt.cmake

@@ -0,0 +1,38 @@
+find_path(fmt_INCLUDE_DIR NAMES fmt/format.h)
+
+if(fmt_INCLUDE_DIR AND EXISTS "${fmt_INCLUDE_DIR}/fmt/format.h")
+  # parse "#define FMT_VERSION 40100" to 4.1.0
+  file(STRINGS "${fmt_INCLUDE_DIR}/fmt/format.h" fmt_VERSION_LINE
+    REGEX "^#define[ \t]+FMT_VERSION[ \t]+[0-9]+$")
+  string(REGEX REPLACE "^#define[ \t]+FMT_VERSION[ \t]+([0-9]+)$"
+    "\\1" fmt_VERSION "${fmt_VERSION_LINE}")
+  foreach(ver "fmt_VERSION_PATCH" "fmt_VERSION_MINOR" "fmt_VERSION_MAJOR")
+    math(EXPR ${ver} "${fmt_VERSION} % 100")
+    math(EXPR fmt_VERSION "(${fmt_VERSION} - ${${ver}}) / 100")
+  endforeach()
+  set(fmt_VERSION_STRING
+      "${fmt_VERSION_MAJOR}.${fmt_VERSION_MINOR}.${fmt_VERSION_PATCH}")
+endif()
+
+find_library(fmt_LIBRARY NAMES fmt)
+
+include(FindPackageHandleStandardArgs)
+find_package_handle_standard_args(fmt
+  FOUND_VAR fmt_FOUND
+  REQUIRED_VARS fmt_INCLUDE_DIR fmt_LIBRARY
+  VERSION_VAR fmt_VERSION_STRING)
+mark_as_advanced(
+  fmt_INCLUDE_DIR
+  fmt_LIBRARY
+  fmt_VERSION_MAJOR
+  fmt_VERSION_MINOR
+  fmt_VERSION_PATCH
+  fmt_VERSION_STRING)
+
+if(fmt_FOUND AND NOT (TARGET fmt::fmt))
+  add_library(fmt::fmt UNKNOWN IMPORTED)
+  set_target_properties(fmt::fmt PROPERTIES
+    INTERFACE_INCLUDE_DIRECTORIES "${fmt_INCLUDE_DIR}"
+    IMPORTED_LINK_INTERFACE_LANGUAGES "CXX"
+    IMPORTED_LOCATION "${fmt_LIBRARY}")
+endif()

src/CMakeLists.txt

@@ -384,7 +384,7 @@ include_directories("${CMAKE_SOURCE_DIR}/src/dmclock/support/src")
 include_directories(SYSTEM "${CMAKE_SOURCE_DIR}/src/googletest/googletest/include")
 
 if(WITH_SEASTAR)
-  find_package(fmt QUIET CONFIG)
+  find_package(fmt 3.0.2)
   if(NOT fmt_FOUND)
     add_subdirectory(fmt)
   endif()