[clang] [analyzer] Model overflow builtins (PR #102602)

[Donát Nagy via cfe-commits]

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@@ -16,21 +16,93 @@
 
 #include "clang/Basic/Builtins.h"
 #include "clang/StaticAnalyzer/Checkers/BuiltinCheckerRegistration.h"
+#include "clang/StaticAnalyzer/Checkers/Taint.h"
 #include "clang/StaticAnalyzer/Core/Checker.h"
 #include "clang/StaticAnalyzer/Core/CheckerManager.h"
 #include "clang/StaticAnalyzer/Core/PathSensitive/CallDescription.h"
 #include "clang/StaticAnalyzer/Core/PathSensitive/CallEvent.h"
 #include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
+#include "clang/StaticAnalyzer/Core/PathSensitive/CheckerHelpers.h"
 #include "clang/StaticAnalyzer/Core/PathSensitive/DynamicExtent.h"
+#include "clang/StaticAnalyzer/Core/PathSensitive/SVals.h"
 
 using namespace clang;
 using namespace ento;
+using namespace taint;
 
 namespace {
 
+QualType getSufficientTypeForOverflowOp(CheckerContext &C, const QualType &T) {
+  // Calling a builtin with a non-integer type result produces compiler error.
+  assert(T->isIntegerType());
+
+  ASTContext &ACtx = C.getASTContext();
+
+  unsigned BitWidth = ACtx.getIntWidth(T);
+  return ACtx.getIntTypeForBitwidth(BitWidth * 2, T->isSignedIntegerType());
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NagyDonat wrote:

What happens if `BitWidth * 2` is too large and there is no standard / semi-standard (like `__int128`) type to represent it? Do we get a compiler error at an earlier step? Does this call crash?

https://github.com/llvm/llvm-project/pull/102602