Allow linking alternate memory management implementations (openstreetmap#454)

With new `CMake CACHE` entry `MALLOC_LIB`, supporting the following values:
* `libc` (default): Use the system's implementation
* `jemalloc`: Use [jemalloc](http://jemalloc.net)
* `mimalloc`: Use [mimalloc](https://github.com/microsoft/mimalloc)
* `tcmalloc`: Use [tcmalloc](https://github.com/google/tcmalloc)

Co-authored-by: Roland Bosa <[email protected]>

Author: hummeltech

CMakeLists.txt

@@ -32,6 +32,8 @@ set(USE_CAIRO ON CACHE BOOL "Add cairo support if available (for `store_ro_compo
 set(USE_CURL ON CACHE BOOL "Add curl support if available (for `store_ro_http_proxy.c` backend)")
 set(USE_MEMCACHED ON CACHE BOOL "Add memcached support if available (for `store_memcached.c` backend)")
 set(USE_RADOS ON CACHE BOOL "Add rados support if available (for `store_rados.c` backend)")
+set(MALLOC_LIB "libc" CACHE STRING "Memory Management Library for `renderd`")
+set_property(CACHE MALLOC_LIB PROPERTY STRINGS "libc" "jemalloc" "mimalloc" "tcmalloc")
 
 #-----------------------------------------------------------------------------
 #
@@ -90,6 +92,20 @@ if(NOT HAVE_POW)
   find_library(MATH_LIBRARY m REQUIRED)
 endif()
 
+if(NOT MALLOC_LIB STREQUAL "libc")
+  message(STATUS "Using '${MALLOC_LIB}' for memory managment")
+  if(MALLOC_LIB STREQUAL "jemalloc")
+    # jemalloc (http://jemalloc.net)
+    find_library(MALLOC_LIBRARY jemalloc REQUIRED)
+  elseif(MALLOC_LIB STREQUAL "mimalloc")
+    # mimalloc (https://github.com/microsoft/mimalloc)
+    find_library(MALLOC_LIBRARY mimalloc REQUIRED)
+  elseif(MALLOC_LIB STREQUAL "tcmalloc")
+    # tcmalloc (https://github.com/google/tcmalloc)
+    find_library(MALLOC_LIBRARY tcmalloc REQUIRED)
+  endif()
+endif()
+
 #-----------------------------------------------------------------------------
 #
 #  Set variables

src/CMakeLists.txt

@@ -41,7 +41,6 @@ set(RENDER_LIBRARIES
   ${COMMON_LIBRARIES}
   ${INIPARSER_LIBRARIES}
   ${MATH_LIBRARY}
-  Threads::Threads
 )
 
 set(STORE_SRCS
@@ -61,6 +60,11 @@ set(STORE_LIBRARIES
   ${LIBRADOS_LIBRARIES}
 )
 
+if(NOT MALLOC_LIB STREQUAL "libc")
+  message(STATUS "Prepending '${MALLOC_LIBRARY}' to RENDER_LIBRARIES")
+  list(PREPEND RENDER_LIBRARIES ${MALLOC_LIBRARY})
+endif()
+
 #-----------------------------------------------------------------------------
 #
 #  Installed targets