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

[alsepkow]

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]

@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;

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[owenca]

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.