fix #12597 (#12604)

lib/system/gc_regions.nim

@@ -378,13 +378,13 @@ proc asgnRefNoCycle(dest: PPointer, src: pointer) {.compilerproc, inline,
   deprecated: "old compiler compat".} = asgnRef(dest, src)
 
 proc alloc(size: Natural): pointer =
-  result = c_malloc(size)
+  result = c_malloc(cast[csize_t](size))
   if result == nil: raiseOutOfMem()
 proc alloc0(size: Natural): pointer =
   result = alloc(size)
   zeroMem(result, size)
 proc realloc(p: pointer, newsize: Natural): pointer =
-  result = c_realloc(p, newsize)
+  result = c_realloc(p, cast[csize_t](newsize))
   if result == nil: raiseOutOfMem()
 proc dealloc(p: pointer) = c_free(p)
 
@@ -401,13 +401,13 @@ proc alloc(r: var MemRegion; size: Natural): pointer =
 proc dealloc(r: var MemRegion; p: pointer) = dealloc(p)
 
 proc allocShared(size: Natural): pointer =
-  result = c_malloc(size)
+  result = c_malloc(cast[csize_t](size))
   if result == nil: raiseOutOfMem()
 proc allocShared0(size: Natural): pointer =
   result = alloc(size)
   zeroMem(result, size)
 proc reallocShared(p: pointer, newsize: Natural): pointer =
-  result = c_realloc(p, newsize)
+  result = c_realloc(p, cast[csize_t](newsize))
   if result == nil: raiseOutOfMem()
 proc deallocShared(p: pointer) = c_free(p)
 

tests/misc/tgcregions.nim

@@ -0,0 +1,6 @@
+discard """
+cmd: "nim c --gc:regions $file"
+"""
+
+# issue #12597
+# it just tests that --gc:regions compiles. Nothing else.   :'(