Suppress all -Wunused-value warnings from macro body expansions.

This is inspired by a number of false positives in real code, including
PR14968. I've added test cases reduced from these false positives to
test/Sema/unused-expr.c, as well as corresponding test cases that pass the
offending expressions as arguments to a no-op macro to ensure that we do warn
there.

This also removes my previous tweak from r166522/r166534, so that we warn on
unused cast expressions in macro arguments.

There were several test cases that were using -Wunused-value to test general
diagnostic emission features; I changed those to use other warnings or warn on
a macro argument expression. I stared at the test case for PR14399 for a while
with Richard Smith and we believe the new test case exercises the same
codepaths as before.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@172696 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 0 insertions, 4 deletions

diff --git a/lib/AST/Expr.cpp b/lib/AST/Expr.cpp
index 45f61fa5c2..4796257c92 100644
--- a/lib/AST/Expr.cpp
+++ b/lib/AST/Expr.cpp
@@ -2100,10 +2100,6 @@ bool Expr::isUnusedResultAWarning(const Expr *&WarnE, SourceLocation &Loc,
       return false;
     }
 
-    // Ignore casts within macro expansions.
-    if (getExprLoc().isMacroID())
-      return CE->getSubExpr()->isUnusedResultAWarning(WarnE, Loc, R1, R2, Ctx);
-
     // If this is a cast to a constructor conversion, check the operand.
     // Otherwise, the result of the cast is unused.
     if (CE->getCastKind() == CK_ConstructorConversion)