Always evaluate the second argument for CHECK() lazily.

This patch is to rename check CHECK and make it a C macro, so that
we can evaluate the second argument lazily.

Differential Revision: https://reviews.llvm.org/D40915

1 files changed, 14 insertions, 12 deletions

diff --git a/lld/include/lld/Common/ErrorHandler.h b/lld/include/lld/Common/ErrorHandler.h
index f43d4520ea9..5f544b88155 100644
--- a/lld/include/lld/Common/ErrorHandler.h
+++ b/lld/include/lld/Common/ErrorHandler.h
@@ -74,7 +74,7 @@ inline uint64_t errorCount() { return errorHandler().ErrorCount; }
 
 LLVM_ATTRIBUTE_NORETURN void exitLld(int Val);
 
-// check() functions are convenient functions to strip errors
+// check functions are convenient functions to strip errors
 // from error-or-value objects.
 template <class T> T check(ErrorOr<T> E) {
   if (auto EC = E.getError())
@@ -88,25 +88,27 @@ template <class T> T check(Expected<T> E) {
   return std::move(*E);
 }
 
-template <class T> T check(ErrorOr<T> E, const Twine &Prefix) {
+template <class T>
+T check2(ErrorOr<T> E, llvm::function_ref<std::string()> Prefix) {
   if (auto EC = E.getError())
-    fatal(Prefix + ": " + EC.message());
-  return std::move(*E);
-}
-
-template <class T> T check(Expected<T> E, const Twine &Prefix) {
-  if (!E)
-    fatal(Prefix + ": " + toString(E.takeError()));
+    fatal(Prefix() + ": " + EC.message());
   return std::move(*E);
 }
 
-// A lazy variant that only allocates error messages when there is an error.
 template <class T>
-T checkLazy(Expected<T> E, llvm::function_ref<std::string()> getPrefix) {
+T check2(Expected<T> E, llvm::function_ref<std::string()> Prefix) {
   if (!E)
-    fatal(getPrefix() + ": " + toString(E.takeError()));
+    fatal(Prefix() + ": " + toString(E.takeError()));
   return std::move(*E);
 }
+
+inline std::string checkToString(const Twine &S) { return S.str(); }
+inline std::string checkToString(std::string S) { return S; }
+inline std::string checkToString(const char *S) { return S; }
+
+// To evaluate the second argument lazily, we use C macro.
+#define CHECK(E, S) check2(E, [&] { return checkToString(S); })
+
 } // namespace lld
 
 #endif