Issue #29392: Prevent crash when passing invalid arguments into msvcrt module.

1 files changed, 41 insertions, 0 deletions

diff --git a/Python/wordcode_helpers.h b/Python/wordcode_helpers.h
new file mode 100644
index 0000000000..b0e3a91776
--- /dev/null
+++ b/Python/wordcode_helpers.h
@@ -0,0 +1,41 @@
+/* This file contains code shared by the compiler and the peephole
+   optimizer.
+ */
+
+#ifdef WORDS_BIGENDIAN
+#  define PACKOPARG(opcode, oparg) ((_Py_CODEUNIT)(((opcode) << 8) | (oparg)))
+#else
+#  define PACKOPARG(opcode, oparg) ((_Py_CODEUNIT)(((oparg) << 8) | (opcode)))
+#endif
+
+/* Minimum number of code units necessary to encode instruction with
+   EXTENDED_ARGs */
+static int
+instrsize(unsigned int oparg)
+{
+    return oparg <= 0xff ? 1 :
+        oparg <= 0xffff ? 2 :
+        oparg <= 0xffffff ? 3 :
+        4;
+}
+
+/* Spits out op/oparg pair using ilen bytes. codestr should be pointed at the
+   desired location of the first EXTENDED_ARG */
+static void
+write_op_arg(_Py_CODEUNIT *codestr, unsigned char opcode,
+    unsigned int oparg, int ilen)
+{
+    switch (ilen) {
+        case 4:
+            *codestr++ = PACKOPARG(EXTENDED_ARG, (oparg >> 24) & 0xff);
+        case 3:
+            *codestr++ = PACKOPARG(EXTENDED_ARG, (oparg >> 16) & 0xff);
+        case 2:
+            *codestr++ = PACKOPARG(EXTENDED_ARG, (oparg >> 8) & 0xff);
+        case 1:
+            *codestr++ = PACKOPARG(opcode, oparg & 0xff);
+            break;
+        default:
+            assert(0);
+    }
+}