Index: clang/include/clang/StaticAnalyzer/Core/AnalyzerOptions.def =================================================================== --- clang/include/clang/StaticAnalyzer/Core/AnalyzerOptions.def +++ clang/include/clang/StaticAnalyzer/Core/AnalyzerOptions.def @@ -314,6 +314,14 @@ "Display the checker name for textual outputs", true) +ANALYZER_OPTION( + bool, ShouldConsiderSingleElementArraysAsFlexibleArrayMembers, + "consider-single-element-arrays-as-flexible-array-members", + "Consider single element arrays as flexible array member candidates. " + "This will prevent the analyzer from assuming that a single element array " + "holds a single element.", + false) + //===----------------------------------------------------------------------===// // Unsigned analyzer options. //===----------------------------------------------------------------------===// Index: clang/lib/StaticAnalyzer/Core/MemRegion.cpp =================================================================== --- clang/lib/StaticAnalyzer/Core/MemRegion.cpp +++ clang/lib/StaticAnalyzer/Core/MemRegion.cpp @@ -28,7 +28,9 @@ #include "clang/Basic/IdentifierTable.h" #include "clang/Basic/LLVM.h" #include "clang/Basic/SourceManager.h" +#include "clang/StaticAnalyzer/Core/AnalyzerOptions.h" #include "clang/StaticAnalyzer/Core/PathSensitive/DynamicExtent.h" +#include "clang/StaticAnalyzer/Core/PathSensitive/ExprEngine.h" #include "clang/StaticAnalyzer/Core/PathSensitive/SValBuilder.h" #include "clang/StaticAnalyzer/Core/PathSensitive/SVals.h" #include "clang/StaticAnalyzer/Core/PathSensitive/SymbolManager.h" @@ -770,9 +772,16 @@ QualType Ty = cast(SR)->getDesugaredValueType(Ctx); const DefinedOrUnknownSVal Size = getElementExtent(Ty, SVB); - // A zero-length array at the end of a struct often stands for dynamically - // allocated extra memory. - const auto isFlexibleArrayMemberCandidate = [this](QualType Ty) -> bool { + // We currently don't model flexible array members (FAMs), which are: + // - int array[]; of IncompleteArrayType + // - int array[0]; of ConstantArrayType with size 0 + // - int array[1]; of ConstantArrayType with size 1 (*) + // (*): Consider single element array object members as FAM candidates only + // if the consider-single-element-arrays-as-flexible-array-members + // analyzer option is true. + // https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html + const auto isFlexibleArrayMemberCandidate = [this, + &SVB](QualType Ty) -> bool { const ArrayType *AT = Ctx.getAsArrayType(Ty); if (!AT) return false; @@ -783,6 +792,15 @@ const llvm::APInt &Size = CAT->getSize(); if (Size.isNullValue()) return true; + + // FIXME: Acquire the AnalyzerOptions in a simpler way. + const AnalyzerOptions &Opts = SVB.getStateManager() + .getOwningEngine() + .getAnalysisManager() + .getAnalyzerOptions(); + if (Opts.ShouldConsiderSingleElementArraysAsFlexibleArrayMembers && + Size.isOneValue()) + return true; } return false; }; Index: clang/test/Analysis/analyzer-config.c =================================================================== --- clang/test/Analysis/analyzer-config.c +++ clang/test/Analysis/analyzer-config.c @@ -31,6 +31,7 @@ // CHECK-NEXT: cfg-rich-constructors = true // CHECK-NEXT: cfg-scopes = false // CHECK-NEXT: cfg-temporary-dtors = true +// CHECK-NEXT: consider-single-element-arrays-as-flexible-array-members = false // CHECK-NEXT: core.CallAndMessage:ArgInitializedness = true // CHECK-NEXT: core.CallAndMessage:ArgPointeeInitializedness = false // CHECK-NEXT: core.CallAndMessage:CXXDeallocationArg = true Index: clang/test/Analysis/flexible-array-members.c =================================================================== --- clang/test/Analysis/flexible-array-members.c +++ clang/test/Analysis/flexible-array-members.c @@ -9,6 +9,11 @@ // RUN: %clang_analyze_cc1 -triple x86_64-linux-gnu -analyzer-checker=core,unix,debug.ExprInspection %s -verify -std=c++14 -x c++ // RUN: %clang_analyze_cc1 -triple x86_64-linux-gnu -analyzer-checker=core,unix,debug.ExprInspection %s -verify -std=c++17 -x c++ +// RUN: %clang_analyze_cc1 -triple x86_64-linux-gnu -analyzer-checker=core,unix,debug.ExprInspection %s -verify -std=c17 \ +// RUN: -analyzer-config consider-single-element-arrays-as-flexible-array-members=true -DSINGLE_ELEMENT_FAMS +// RUN: %clang_analyze_cc1 -triple x86_64-linux-gnu -analyzer-checker=core,unix,debug.ExprInspection %s -verify -std=c++17 -x c++ \ +// RUN: -analyzer-config consider-single-element-arrays-as-flexible-array-members=true -DSINGLE_ELEMENT_FAMS + typedef __typeof(sizeof(int)) size_t; size_t clang_analyzer_getExtent(void *); void clang_analyzer_dump(size_t); @@ -75,6 +80,26 @@ int data[1]; } FAM; +#ifdef SINGLE_ELEMENT_FAMS + FAM likely_fam; + clang_analyzer_dump(clang_analyzer_getExtent(&likely_fam)); + clang_analyzer_dump(clang_analyzer_getExtent(likely_fam.data)); + // expected-warning@-2 {{8 S64b}} + // expected-warning@-2 {{Unknown}} + + FAM *p = (FAM *)alloca(sizeof(FAM)); + clang_analyzer_dump(clang_analyzer_getExtent(p)); + clang_analyzer_dump(clang_analyzer_getExtent(p->data)); + // expected-warning@-2 {{8 U64b}} + // expected-warning@-2 {{Unknown}} + + FAM *q = (FAM *)malloc(sizeof(FAM)); + clang_analyzer_dump(clang_analyzer_getExtent(q)); + clang_analyzer_dump(clang_analyzer_getExtent(q->data)); + // expected-warning@-2 {{8 U64b}} + // expected-warning@-2 {{Unknown}} + free(q); +#else FAM likely_fam; clang_analyzer_dump(clang_analyzer_getExtent(&likely_fam)); clang_analyzer_dump(clang_analyzer_getExtent(likely_fam.data)); @@ -93,4 +118,5 @@ // expected-warning@-2 {{8 U64b}} // expected-warning@-2 {{4 S64b}} free(q); +#endif }