Defer generation of tentative definitions.

 - PR3980.

 - <rdar://problem/6762287> [irgen] crash when generating tentative
   definition of incomplete structure

 - This also avoids creating common definitions for things which are
   later overwritten.

 - XFAIL'ed external-defs.c, it isn't completing types properly yet.

llvm-svn: 69231

1 files changed, 28 insertions, 0 deletions

diff --git a/clang/test/CodeGen/tentative-decls.c b/clang/test/CodeGen/tentative-decls.c
new file mode 100644
index 00000000000..4604f2f4297
--- /dev/null
+++ b/clang/test/CodeGen/tentative-decls.c
@@ -0,0 +1,28 @@
+// RUN: clang-cc -emit-llvm -o %t %s &&
+
+// RUN: grep '@r = common global \[1 x .*\] zeroinitializer' %t &&
+
+int r[];
+int (*a)[] = &r;
+
+struct s0;
+struct s0 x;
+// RUN: grep '@x = common global .struct.s0 zeroinitializer' %t &&
+
+struct s0 y;
+// RUN: grep '@y = common global .struct.s0 zeroinitializer' %t &&
+struct s0 *f0() {
+  return &y;
+}
+
+struct s0 {
+  int x;
+};
+
+// RUN: grep '@b = common global \[1 x .*\] zeroinitializer' %t &&
+int b[];
+int *f1() {
+  return b;
+}
+
+// RUN: true