1 files changed, 36 insertions, 0 deletions
diff --git a/tests/mmaptest.nim b/tests/mmaptest.nim
new file mode 100644
index 000000000..33010606f
--- /dev/null
+++ b/tests/mmaptest.nim
@@ -0,0 +1,36 @@
+# Small test program to test for mmap() weirdnesses
+
+import system/ansi_c
+import posix
+
+proc osAllocPages(size: int): pointer {.inline.} =
+  result = mmap(nil, size, PROT_READ or PROT_WRITE,
+                         MAP_PRIVATE or MAP_ANONYMOUS, -1, 0)
+  if result == nil or result == cast[pointer](-1):
+    quit 1
+  cfprintf(c_stdout, "allocated pages %p..%p\n", result,
+                     cast[int](result) + size)
+
+proc osDeallocPages(p: pointer, size: int) {.inline} =
+  cfprintf(c_stdout, "freed pages %p..%p\n", p, cast[int](p) + size)
+  discard munmap(p, size-1)
+
+proc `+!!`(p: pointer, size: int): pointer {.inline.} =
+  result = cast[pointer](cast[int](p) + size)
+
+const
+  PageShift = when defined(nimPage256) or defined(cpu16): 8
+              elif defined(nimPage512): 9
+              elif defined(nimPage1k): 10
+              else: 12 # \ # my tests showed no improvements for using larger page sizes.
+
+  PageSize = 1 shl PageShift
+
+var p = osAllocPages(3 * PageSize)
+
+osDeallocPages(p, PageSize)
+# If this fails the OS has freed the whole block starting at 'p':
+echo(cast[ptr int](p +!! (PageSize*2))[])
+
+osDeallocPages(p +!! PageSize*2, PageSize)
+osDeallocPages(p +!! PageSize, PageSize)