Address a handful of C4146 compiler warnings where literals can be replaced with std::numeric_limits #147623

alsepkow · 2025-07-09T00:22:47Z

This PR addresses instances of compiler warning C4146 that can be replaced with std::numeric_limits. Specifically, these are cases where a literal such as '-1ULL' was used to assign a value to a uint64_t variable. The intent is much cleaner if we use the appropriate std::numeric_limits value::max() for these cases.

Addresses #147439

llvmbot · 2025-07-09T00:23:19Z

@llvm/pr-subscribers-clang

@llvm/pr-subscribers-clang-format

Author: Alex Sepkowski (alsepkow)

Changes

This PR addresses instances of compiler warning C4146 that can be replaced with std::numeric_limits. Specifically, these are cases where a literal such as '-1ULL' was used to assign a value to a uint64_t variable. The intent is much cleaner if we use the appropriate std::numeric_limits value<Type>::max() for these cases.

Addresses #147439

Full diff: https://github.com/llvm/llvm-project/pull/147623.diff

4 Files Affected:

(modified) clang/lib/AST/ExprConstant.cpp (+2-2)
(modified) clang/lib/Format/Format.cpp (+5-2)
(modified) clang/lib/Lex/Lexer.cpp (+2-1)
(modified) clang/lib/Sema/SemaExpr.cpp (+4-2)

diff --git a/clang/lib/AST/ExprConstant.cpp b/clang/lib/AST/ExprConstant.cpp
index 60c658a8d8f99..5d399a3c75ca8 100644
--- a/clang/lib/AST/ExprConstant.cpp
+++ b/clang/lib/AST/ExprConstant.cpp
@@ -1428,11 +1428,11 @@ namespace {
     }
     bool destroy(bool RunDestructors = true) {
       bool OK = cleanup(Info, RunDestructors, OldStackSize);
-      OldStackSize = -1U;
+      OldStackSize = std::numeric_limits<unsigned>::max();
       return OK;
     }
     ~ScopeRAII() {
-      if (OldStackSize != -1U)
+      if (OldStackSize != std::numeric_limits<unsigned>::max())
         destroy(false);
       // Body moved to a static method to encourage the compiler to inline away
       // instances of this class.
diff --git a/clang/lib/Format/Format.cpp b/clang/lib/Format/Format.cpp
index f0412cddc6f19..5f5a5d9d8a571 100644
--- a/clang/lib/Format/Format.cpp
+++ b/clang/lib/Format/Format.cpp
@@ -22,7 +22,9 @@
 #include "UnwrappedLineFormatter.h"
 #include "UsingDeclarationsSorter.h"
 #include "clang/Tooling/Inclusions/HeaderIncludes.h"
+
 #include "llvm/ADT/Sequence.h"
+#include <limits>
 
 #define DEBUG_TYPE "format-formatter"
 
@@ -777,7 +779,7 @@ template <> struct MappingTraits<FormatStyle::SpacesInLineComment> {
     IO.mapOptional("Maximum", signedMaximum);
     Space.Maximum = static_cast<unsigned>(signedMaximum);
 
-    if (Space.Maximum != -1u)
+    if (Space.Maximum != std::numeric_limits<unsigned>::max())
       Space.Minimum = std::min(Space.Minimum, Space.Maximum);
   }
 };
@@ -1672,7 +1674,8 @@ FormatStyle getLLVMStyle(FormatStyle::LanguageKind Language) {
   LLVMStyle.SpacesBeforeTrailingComments = 1;
   LLVMStyle.SpacesInAngles = FormatStyle::SIAS_Never;
   LLVMStyle.SpacesInContainerLiterals = true;
-  LLVMStyle.SpacesInLineCommentPrefix = {/*Minimum=*/1, /*Maximum=*/-1u};
+  LLVMStyle.SpacesInLineCommentPrefix = {
+      /*Minimum=*/1, /*Maximum=*/std::numeric_limits<unsigned>::max()};
   LLVMStyle.SpacesInParens = FormatStyle::SIPO_Never;
   LLVMStyle.SpacesInSquareBrackets = false;
   LLVMStyle.Standard = FormatStyle::LS_Latest;
diff --git a/clang/lib/Lex/Lexer.cpp b/clang/lib/Lex/Lexer.cpp
index 78988e928a689..1f695b4a8676c 100644
--- a/clang/lib/Lex/Lexer.cpp
+++ b/clang/lib/Lex/Lexer.cpp
@@ -41,6 +41,7 @@
 #include <cstddef>
 #include <cstdint>
 #include <cstring>
+#include <limits>
 #include <optional>
 #include <string>
 #include <tuple>
@@ -3456,7 +3457,7 @@ std::optional<uint32_t> Lexer::tryReadNumericUCN(const char *&StartPtr,
     }
 
     unsigned Value = llvm::hexDigitValue(C);
-    if (Value == -1U) {
+    if (Value == std::numeric_limits<unsigned>::max()) {
       if (!Delimited)
         break;
       if (Diagnose)
diff --git a/clang/lib/Sema/SemaExpr.cpp b/clang/lib/Sema/SemaExpr.cpp
index 3c3d29c415249..fcc015be1d5f4 100644
--- a/clang/lib/Sema/SemaExpr.cpp
+++ b/clang/lib/Sema/SemaExpr.cpp
@@ -65,6 +65,7 @@
 #include "llvm/Support/SaveAndRestore.h"
 #include "llvm/Support/TimeProfiler.h"
 #include "llvm/Support/TypeSize.h"
+#include <limits>
 #include <optional>
 
 using namespace clang;
@@ -1906,7 +1907,7 @@ ExprResult Sema::CreateGenericSelectionExpr(
   }
 
   SmallVector<unsigned, 1> CompatIndices;
-  unsigned DefaultIndex = -1U;
+  unsigned DefaultIndex = std::numeric_limits<unsigned>::max();
   // Look at the canonical type of the controlling expression in case it was a
   // deduced type like __auto_type. However, when issuing diagnostics, use the
   // type the user wrote in source rather than the canonical one.
@@ -1961,7 +1962,8 @@ ExprResult Sema::CreateGenericSelectionExpr(
   // C11 6.5.1.1p2 "If a generic selection has no default generic association,
   // its controlling expression shall have type compatible with exactly one of
   // the types named in its generic association list."
-  if (DefaultIndex == -1U && CompatIndices.size() == 0) {
+  if (DefaultIndex == std::numeric_limits<unsigned>::max() &&
+      CompatIndices.size() == 0) {
     auto P = GetControllingRangeAndType(ControllingExpr, ControllingType);
     SourceRange SR = P.first;
     Diag(SR.getBegin(), diag::err_generic_sel_no_match) << SR << P.second;

github-actions · 2025-07-09T00:24:28Z

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owenca · 2025-07-09T01:14:44Z

clang/lib/Format/Format.cpp

@@ -777,7 +779,7 @@ template <> struct MappingTraits<FormatStyle::SpacesInLineComment> {
    IO.mapOptional("Maximum", signedMaximum);
    Space.Maximum = static_cast<unsigned>(signedMaximum);

-    if (Space.Maximum != -1u)
+    if (Space.Maximum != std::numeric_limits<unsigned>::max())


Suggested change

if (Space.Maximum != std::numeric_limits<unsigned>::max())

if (Space.Maximum < UINT_MAX)

as that's what's used elsewhere in the file.

On further consideration, I think it would be cleaner to stay consistent with using numeric_limits for all of the updates. And given that there are only a handful of UINT_MAX cases in this file I've swapped them to use numeric_limits for consistency. That would be the preferred choice if this were new code anyways.

bogner

I agree that this improves the clarity here. LGTM!

Swap to UINT_MAX to match formatting of the rest of the file. Co-authored-by: Owen Pan <owenpiano@gmail.com>

clang/lib/Format/Format.cpp

bogner · 2025-07-09T23:14:57Z

I went ahead and merged this for you. Thanks!

alsepkow added 5 commits July 8, 2025 16:17

Numeric limits in ExprConstant.cpp

7e1c62f

Numeric limits in Format.cpp

98197ad

Numeric limits in Lexer.cpp

a073761

Numeric limits in SemaExpr.cpp

2a479e1

Clang-format previous changes

46d1485

llvmbot added clang Clang issues not falling into any other category clang-format clang:frontend Language frontend issues, e.g. anything involving "Sema" labels Jul 9, 2025

owenca reviewed Jul 9, 2025

View reviewed changes

bogner approved these changes Jul 9, 2025

View reviewed changes

Update clang/lib/Format/Format.cpp

9aa8125

Swap to UINT_MAX to match formatting of the rest of the file. Co-authored-by: Owen Pan <owenpiano@gmail.com>

bob80905 approved these changes Jul 9, 2025

View reviewed changes

Update to use numeric_limits across Format.cpp instead of UINT_MAX

013a5aa

tex3d reviewed Jul 9, 2025

View reviewed changes

clang/lib/Format/Format.cpp Outdated Show resolved Hide resolved

bogner merged commit 7c16a31 into llvm:main Jul 9, 2025
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Address a handful of C4146 compiler warnings where literals can be replaced with std::numeric_limits #147623

Address a handful of C4146 compiler warnings where literals can be replaced with std::numeric_limits #147623

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	if (Space.Maximum != std::numeric_limits<unsigned>::max())
	if (Space.Maximum < UINT_MAX)

Address a handful of C4146 compiler warnings where literals can be replaced with std::numeric_limits #147623

Address a handful of C4146 compiler warnings where literals can be replaced with std::numeric_limits #147623

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