Add memcmp() function to stdlib/mem.jou (#748)

compiler/tokenizer.jou

@@ -153,10 +153,6 @@ def flip_paren(c: byte) -> byte:
             assert False
 
 
-# TODO: put to stdlib
-declare memcmp(s1: void*, s2: void*, n: long) -> int
-
-
 def detect_banned_whitespace_characters(last_3_bytes: byte[3]) -> byte*:
     last_2_bytes = [last_3_bytes[1], last_3_bytes[2]]
 

compiler/uvg_analyze.jou

@@ -169,10 +169,6 @@ def update_statuses_based_on_instructions(uvg: Uvg*, statuses: VarStatus*, block
                 statuses[ins->var] = VarStatus.DontAnalyze
 
 
-# TODO: put to stdlib
-declare memcmp(s1: void*, s2: void*, n: long) -> int
-
-
 def analyze_block(uvg: Uvg*, statuses_at_end: VarStatus**, blockidx: int, warn: bool) -> bool:
     statuses = build_statuses_at_start_of_block(uvg, statuses_at_end, blockidx)
     update_statuses_based_on_instructions(uvg, statuses, uvg->blocks[blockidx], warn)

stdlib/mem.jou

@@ -32,6 +32,20 @@ declare memcpy(dest: void*, source: void*, size: long) -> void*  # copy memory,
 @public
 declare memmove(dest: void*, source: void*, size: long) -> void*  # copy memory, overlaps are ok
 
+# Compare two memory regions of the same size. Return 0 if they contain the
+# same bytes, nonzero if different bytes.
+#
+# This can be used to e.g. check if two arrays of ints are equal:
+#
+#   a = [1, 2, 3]
+#   b = [1, 2, 4]
+#   if memcmp(a, b, sizeof(a)) != 0:
+#       printf("Different\n")
+#
+# This is somewhat similar to strcmp() in stdlib/str.jou.
+@public
+declare memcmp(a: void*, b: void*, size: long) -> int
+
 # Swaps the contents of two memory regions of the same size.
 # This does nothing if the same memory region is passed twice.
 # This probably doesn't do what you want if the memory regions overlap in some other way.

tests/should_succeed/memlibtest.jou

@@ -12,4 +12,12 @@ def main() -> int:
     memswap(&a, &a, sizeof(a))  # does nothing
     printf("%d %d\n", a, b)   # Output: 456 123
 
+    arr1 = [1, 2, 3]
+    arr2 = [1, 2, 3]
+    printf("%d\n", memcmp(arr1, arr2, sizeof(arr1)))  # Output: 0
+    arr1[1]++
+    printf("%d\n", memcmp(arr1, arr2, sizeof(arr1)))  # Output: 1
+    arr2[0]++
+    printf("%d\n", memcmp(arr1, arr2, sizeof(arr1)))  # Output: -1
+
     return 0