[clang] [clang][analyzer] Add allocation failure modeling to DynamicMemoryModeling (PR #205371)

[Balázs Benics via cfe-commits]

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@@ -663,6 +672,22 @@ class MallocChecker
                                              SVal Init, ProgramStateRef State,
                                              AllocationFamily Family) const;
 
+  /// Models a non-successful memory allocation.
+  /// Can be used if the allocation function may return null on failure when the
+  /// size to be allocated is non-zero.
+  ///
+  /// \param [in] Call The expression that allocates memory.
+  /// \param [in] SizeArgI1 Index of the argument that specifies the allocation
+  /// size or count. -1 if not applicable.
+  /// \param [in] SizeArgI2 Index of another argument that specifies allocation
+  /// size (i. e. "element size"). -1 if not applicable.
+  /// \param [in] State The \c ProgramState right before allocation.
+  /// \returns The ProgramState right after an unsuccessful allocation.
+  [[nodiscard]] ProgramStateRef FailedAlloc(CheckerContext &C,
+                                            const CallEvent &Call,
+                                            int SizeArgI1, int SizeArgI2,
+                                            ProgramStateRef State) const;
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steakhal wrote:

I was reading this PR again, and I think we could make it better.
How about moving the SizeArgs after State?
Then we could pass an `llvm::ArrayRef<unsigned> SizeArgIndexes= {}`
Then at the callsites, you could leave it empty if none should be passed. Otherwise pass `{1}` or whatever.
WDYT? @balazske 

https://github.com/llvm/llvm-project/pull/205371