[ms] Fix mangling of string literals used to initialize arrays larger or smaller than the literal

A Chromium developer reported a bug which turned out to be a mangling
collision between these two literals:

  char s[] = "foo";
  char t[32] = "foo";

They may look the same, but for the initialization of t we will (under
some circumstances) use a literal that's extended with zeros, and
both the length and those zeros should be accounted for by the mangling.

This actually makes the mangling code simpler: where it previously had
special logic for null terminators, which are not part of the
StringLiteral, that is now covered by the general algorithm.

(The problem was reported at https://crbug.com/857442)

Differential Revision: https://reviews.llvm.org/D48928

llvm-svn: 336415

1 files changed, 10 insertions, 0 deletions

diff --git a/clang/test/CodeGen/mangle-ms-string-literals.c b/clang/test/CodeGen/mangle-ms-string-literals.c
new file mode 100644
index 00000000000..41dd78c1fa7
--- /dev/null
+++ b/clang/test/CodeGen/mangle-ms-string-literals.c
@@ -0,0 +1,10 @@
+// RUN: %clang_cc1 -x c -emit-llvm %s -o - -triple=i386-pc-win32 | FileCheck %s
+// RUN: %clang_cc1 -x c -emit-llvm %s -o - -triple=x86_64-pc-win32 | FileCheck %s
+
+void crbug857442(int x) {
+  // Make sure to handle truncated or padded literals. The truncation is only valid in C.
+  struct {int x; char s[2]; } truncatedAscii = {x, "hello"};
+  // CHECK: "??_C@_01CONKJJHI@he@"
+  struct {int x; char s[16]; } paddedAscii = {x, "hello"};
+  // CHECK: "??_C@_0BA@EAAINDNC@hello?$AA?$AA?$AA?$AA?$AA?$AA?$AA?$AA?$AA?$AA?$AA@"
+}