calculate the address of the size in a different way

ngoldbaum · ngoldbaum · commit 7d0c58f5d2a3 · 2023-11-01T12:49:53.000-06:00
diff --git a/stringdtype/stringdtype/src/static_string.c b/stringdtype/stringdtype/src/static_string.c
@@ -314,7 +314,8 @@ heap_or_arena_allocate(npy_string_allocator *allocator,
         }
         else {
             // not necessarily memory-aligned, so need to use memcpy
-            memcpy(&alloc_size, ((size_t *)buf - 1), sizeof(size_t));
+            char *size_loc = (char *)((uintptr_t)buf - sizeof(size_t));
+            memcpy(&alloc_size, size_loc, sizeof(size_t));
         }
         if (size <= alloc_size) {
             // we have room!

Original file line number	Diff line number	Diff line change
`@@ -314,7 +314,8 @@ heap_or_arena_allocate(npy_string_allocator *allocator,`
`314`	`314`	`}`
`315`	`315`	`else {`
`316`	`316`	`// not necessarily memory-aligned, so need to use memcpy`
`317`		`- memcpy(&alloc_size, ((size_t *)buf - 1), sizeof(size_t));`
	`317`	`+ char size_loc = (char )((uintptr_t)buf - sizeof(size_t));`
	`318`	`+ memcpy(&alloc_size, size_loc, sizeof(size_t));`
`318`	`319`	`}`
`319`	`320`	`if (size <= alloc_size) {`
`320`	`321`	`// we have room!`