[lld] r319922 - Add a checkLazy error checking variant.

[Rafael Espindola via llvm-commits]

Author: rafael
Date: Wed Dec  6 10:52:13 2017
New Revision: 319922

URL: http://llvm.org/viewvc/llvm-project?rev=319922&view=rev
Log:
Add a checkLazy error checking variant.

This avoids allocating the error message when there is no error that
check requires.

It avoids the code duplication of inlining check.

Modified:
    lld/trunk/ELF/InputFiles.cpp
    lld/trunk/include/lld/Common/ErrorHandler.h

Modified: lld/trunk/ELF/InputFiles.cpp
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/InputFiles.cpp?rev=319922&r1=319921&r2=319922&view=diff
==============================================================================
--- lld/trunk/ELF/InputFiles.cpp (original)
+++ lld/trunk/ELF/InputFiles.cpp Wed Dec  6 10:52:13 2017
@@ -209,10 +209,8 @@ typename ELFT::SymRange ELFFileBase<ELFT
 
 template <class ELFT>
 uint32_t ELFFileBase<ELFT>::getSectionIndex(const Elf_Sym &Sym) const {
-  auto RetOrErr = getObj().getSectionIndex(&Sym, ELFSyms, SymtabSHNDX);
-  if (RetOrErr)
-    return *RetOrErr;
-  fatal(toString(this) + ": " + toString(RetOrErr.takeError()));
+  return checkLazy(getObj().getSectionIndex(&Sym, ELFSyms, SymtabSHNDX),
+                   [=]() { return toString(this); });
 }
 
 template <class ELFT>
@@ -642,10 +640,8 @@ template <class ELFT> Symbol *ObjFile<EL
     return make<Defined>(this, Name, Binding, StOther, Type, Value, Size, Sec);
   }
 
-  auto NameOrErr = Sym->getName(this->StringTable);
-  if (!NameOrErr)
-    fatal(toString(this) + ": " + toString(NameOrErr.takeError()));
-  StringRef Name = *NameOrErr;
+  StringRef Name = checkLazy(Sym->getName(this->StringTable),
+                             [=]() { return toString(this); });
 
   switch (Sym->st_shndx) {
   case SHN_UNDEF:

Modified: lld/trunk/include/lld/Common/ErrorHandler.h
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/include/lld/Common/ErrorHandler.h?rev=319922&r1=319921&r2=319922&view=diff
==============================================================================
--- lld/trunk/include/lld/Common/ErrorHandler.h (original)
+++ lld/trunk/include/lld/Common/ErrorHandler.h Wed Dec  6 10:52:13 2017
@@ -30,6 +30,7 @@
 
 #include "lld/Common/LLVM.h"
 
+#include "llvm/ADT/STLExtras.h"
 #include "llvm/Support/Error.h"
 #include "llvm/Support/FileOutputBuffer.h"
 
@@ -99,6 +100,13 @@ template <class T> T check(Expected<T> E
   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) {
+  if (!E)
+    fatal(getPrefix() + ": " + toString(E.takeError()));
+  return std::move(*E);
+}
 } // namespace lld
 
 #endif