From b529d830b3b1667157da92ab0b5c32e1acfafbab Mon Sep 17 00:00:00 2001
From: Eli Friedman <eli.friedman@gmail.com>
Date: Tue, 2 Sep 2008 09:37:00 +0000
Subject: [PATCH] Fix for PR2747: allow pointer->int casts with a null base;
 these are offset-of-like expressions.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@55627 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Sema/SemaDecl.cpp | 7 +++++++
 test/Sema/init.c      | 8 ++++++++
 2 files changed, 15 insertions(+)

diff --git a/lib/Sema/SemaDecl.cpp b/lib/Sema/SemaDecl.cpp
index 7e60da5af3..564f530191 100644
--- a/lib/Sema/SemaDecl.cpp
+++ b/lib/Sema/SemaDecl.cpp
@@ -1163,6 +1163,13 @@ bool Sema::CheckArithmeticConstantExpression(const Expr* Init) {
     if (SubExpr->getType()->isArithmeticType())
       return CheckArithmeticConstantExpression(SubExpr);
 
+    if (SubExpr->getType()->isPointerType()) {
+      const Expr* Base = FindExpressionBaseAddress(SubExpr);
+      // If the pointer has a null base, this is an offsetof-like construct
+      if (!Base)
+        return CheckAddressConstantExpression(SubExpr);
+    }
+
     Diag(Init->getExprLoc(),
          diag::err_init_element_not_constant, Init->getSourceRange());
     return true;
diff --git a/test/Sema/init.c b/test/Sema/init.c
index 964118ce02..10eed146a0 100644
--- a/test/Sema/init.c
+++ b/test/Sema/init.c
@@ -58,3 +58,11 @@ union { float f; unsigned u; } u = { 1.0f };
 int f3(int x) { return x; }
 typedef void (*vfunc)(void);
 void *bar = (vfunc) f3;
+
+// PR2747
+struct sym_reg {
+        char nc_gpreg;
+};
+int sym_fw1a_scr[] = {
+           ((int)(&((struct sym_reg *)0)->nc_gpreg)) & 0
+};
-- 
2.40.0