[PATCH] D91968: llvm/ADT/StringExtras.h hexDigitValue - Init of integer buffer

Jerker B├Ąck via Phabricator via llvm-commits llvm-commits at lists.llvm.org
Mon Nov 23 07:41:34 PST 2020


jerker.back created this revision.
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jerker.back requested review of this revision.

Hi,

In the header //`StringExtras.h`//, function //`hexDigitValue`//

due to the expression

  LUT[i] = -1U;

my compiler gives me

  error C4146: unary minus operator applied to unsigned type, result still unsigned

This is a warning turned into an error by a default compiler switch
The patch gives one solution which I believe also could be more efficient

Thanks


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D91968

Files:
  llvm/include/llvm/ADT/StringExtras.h


Index: llvm/include/llvm/ADT/StringExtras.h
===================================================================
--- llvm/include/llvm/ADT/StringExtras.h
+++ llvm/include/llvm/ADT/StringExtras.h
@@ -67,11 +67,8 @@
 /// If \p C is not a valid hex digit, -1U is returned.
 inline unsigned hexDigitValue(char C) {
   struct HexTable {
-    unsigned LUT[255] = {};
+    unsigned LUT[255] = {static_cast<unsigned>(-1)};
     constexpr HexTable() {
-      // Default initialize everything to invalid.
-      for (int i = 0; i < 255; ++i)
-        LUT[i] = -1U;
       // Initialize `0`-`9`.
       for (int i = 0; i < 10; ++i)
         LUT['0' + i] = i;


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