Expose MIN_ALLOC_{,STEP}_SIZE through cmake

microsoft · Jan 5, 2024 · ab87e2b · ab87e2b
1 parent 0cdbe59
commit ab87e2b
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Showing 2 changed files with 22 additions and 2 deletions.
diff --git a/CMakeLists.txt b/CMakeLists.txt
@@ -62,6 +62,9 @@ if (SNMALLOC_SANITIZER)
   message(STATUS "Using sanitizer=${SNMALLOC_SANITIZER}")
 endif()
 
+set(SNMALLOC_MIN_ALLOC_SIZE "" CACHE STRING "Minimum allocation bytes (power of 2)")
+set(SNMALLOC_MIN_ALLOC_STEP_SIZE "" CACHE STRING "Minimum allocation step (power of 2)")
+
 if(MSVC AND SNMALLOC_STATIC_LIBRARY AND (SNMALLOC_STATIC_LIBRARY_PREFIX STREQUAL ""))
   message(FATAL_ERROR "Empty static library prefix not supported on MSVC")
 endif()
@@ -226,6 +229,11 @@ endif()
 function(add_as_define FLAG)
   target_compile_definitions(snmalloc INTERFACE $<$<BOOL:${${FLAG}}>:${FLAG}>)
 endfunction()
+function(add_as_define_value KEY)
+  if (NOT ${${KEY}} STREQUAL "")
+    target_compile_definitions(snmalloc INTERFACE ${KEY}=${${KEY}})
+  endif ()
+endfunction()
 
 add_as_define(SNMALLOC_QEMU_WORKAROUND)
 add_as_define(SNMALLOC_TRACING)
@@ -238,6 +246,8 @@ endif()
 if (SNMALLOC_NO_REALLOCARR)
   add_as_define(SNMALLOC_NO_REALLOCARR)
 endif()
+add_as_define_value(SNMALLOC_MIN_ALLOC_SIZE)
+add_as_define_value(SNMALLOC_MIN_ALLOC_STEP_SIZE)
 
 target_compile_definitions(snmalloc INTERFACE $<$<BOOL:CONST_QUALIFIED_MALLOC_USABLE_SIZE>:MALLOC_USABLE_SIZE_QUALIFIER=const>)
 

diff --git a/src/snmalloc/ds/allocconfig.h b/src/snmalloc/ds/allocconfig.h
@@ -21,7 +21,12 @@ namespace snmalloc
   static constexpr size_t CACHELINE_SIZE = 64;
 
   /// The "machine epsilon" for the small sizeclass machinery.
-  static constexpr size_t MIN_ALLOC_STEP_SIZE = 2 * sizeof(void*);
+  static constexpr size_t MIN_ALLOC_STEP_SIZE =
+#if defined(SNMALLOC_MIN_ALLOC_STEP_SIZE)
+    SNMALLOC_MIN_ALLOC_STEP_SIZE;
+#else
+    2 * sizeof(void*);
+#endif
 
   /// Derived from MIN_ALLOC_STEP_SIZE
   static constexpr size_t MIN_ALLOC_STEP_BITS =
@@ -34,7 +39,12 @@ namespace snmalloc
    * smaller than MIN_ALLOC_SIZE), which may be useful if MIN_ALLOC_SIZE must
    * be large or not a power of two, those smaller size classes will be unused.
    */
-  static constexpr size_t MIN_ALLOC_SIZE = 2 * sizeof(void*);
+  static constexpr size_t MIN_ALLOC_SIZE =
+#if defined(SNMALLOC_MIN_ALLOC_SIZE)
+    SNMALLOC_MIN_ALLOC_SIZE;
+#else
+    2 * sizeof(void*);
+#endif
 
   // Minimum slab size.
 #if defined(SNMALLOC_QEMU_WORKAROUND) && defined(SNMALLOC_VA_BITS_64)