[PATCH] D153954: [WIP][clang][analyzer] Relax alpha.cplusplus.EnumCastOutOfRange checker

[Endre Fülöp via Phabricator via cfe-commits]

gamesh411 updated this revision to Diff 543413.
gamesh411 edited the summary of this revision.
gamesh411 added a comment.

The checker now retains the original detection logic, but only whitelists empty
enums.

As a future step the checker is moved into the optin package.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D153954/new/

https://reviews.llvm.org/D153954

Files:
  clang/lib/StaticAnalyzer/Checkers/EnumCastOutOfRangeChecker.cpp
  clang/test/Analysis/enum-cast-out-of-range.cpp


Index: clang/test/Analysis/enum-cast-out-of-range.cpp
===================================================================
--- clang/test/Analysis/enum-cast-out-of-range.cpp
+++ clang/test/Analysis/enum-cast-out-of-range.cpp
@@ -198,3 +198,20 @@
   s.E = static_cast<unscoped_unspecified_t>(4); // OK.
   s.E = static_cast<unscoped_unspecified_t>(5); // expected-warning {{The value provided to the cast expression is not in the valid range of values for the enum}}
 }
+
+
+enum class empty_unfixed {};
+
+enum class empty_fixed: char {};
+
+enum class empty_fixed_unsigned: unsigned char {};
+
+void ignore_unused(...);
+
+void empty_enums_init_with_zero_should_not_warn() {
+  empty_unfixed eu = static_cast<empty_unfixed>(0); //should always be OK to zero initialize any enum
+  empty_fixed ef = static_cast<empty_fixed>(0);
+  empty_fixed_unsigned efu = static_cast<empty_fixed_unsigned>(0);
+
+  ignore_unused(eu, ef, efu);
+}
Index: clang/lib/StaticAnalyzer/Checkers/EnumCastOutOfRangeChecker.cpp
===================================================================
--- clang/lib/StaticAnalyzer/Checkers/EnumCastOutOfRangeChecker.cpp
+++ clang/lib/StaticAnalyzer/Checkers/EnumCastOutOfRangeChecker.cpp
@@ -129,6 +129,14 @@
   const EnumDecl *ED = T->castAs<EnumType>()->getDecl();
 
   EnumValueVector DeclValues = getDeclValuesForEnum(ED);
+
+  // If the declarator list is empty, bail out.
+  // Every initialization an enum with a fixed underlying type but without any
+  // enumerators would produce a warning if we were to continue at this point.
+  // The most notable example is std::byte in the C++17 standard library.
+  if (DeclValues.size() == 0)
+    return;
+
   // Check if any of the enum values possibly match.
   bool PossibleValueMatch = llvm::any_of(
       DeclValues, ConstraintBasedEQEvaluator(C, *ValueToCast));


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