[PATCH] D140387: [clang][analyzer] Add stream related functions to StdLibraryFunctionsChecker.

[Kristóf Umann via Phabricator via cfe-commits]

Szelethus added a comment.

In D140387#4021806 <https://reviews.llvm.org/D140387#4021806>, @Szelethus wrote:

> Would be possible to test the errno specific changes as well?

I suppose the tests are done in the followup patch mostly?



================
Comment at: clang/lib/StaticAnalyzer/Checkers/ErrnoModeling.cpp:310
+  const MemRegion *ErrnoR = State->get<ErrnoRegion>();
+  if (!ErrnoR)
+    return State;
----------------
balazske wrote:
> Szelethus wrote:
> > When can this occur? Maybe we can turn this early return to an assert -- when `ModelPOSIX` is true, this mustn't be null (if what I'm saying is correct).
> I am not totally sure that `errno` is found always (definition of `errno` is encountered) if a summary for a standard function is added. The standard function in itself must be there, otherwise no summary is added and this function should not be called. But definition of `errno` may reside in other header (errno.h) that is probably not included in the translation unit. If the errno definition is not found the `ErrnoRegion` is not set (the checker may still turned be on but does nothing, but these functions are allowed to be called). Existence of `errno` is not even dependent on `ModelPOSIX`, `errno` is defined in the (non POSIX) C standard.
Very well, I'm sold.


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Comment at: clang/lib/StaticAnalyzer/Checkers/StdLibraryFunctionsChecker.cpp:1705-1707
+          // FIXME: It should be allowed to have a null buffer if any of
+          // args 1 or 2 are zero. Remove NotNull check of arg 0, add a check
+          // for non-null buffer if non-zero size to BufferSizeConstraint?
----------------
balazske wrote:
> Szelethus wrote:
> > Maybe `StreamChecker` could take over the handling of that case? Seems like it also warns about the nullness of the first `fread` parameter.
> The current approach was that the NULL argument warning is generated by one checker only, `StreamChecker` or this checker. The NULL check is already built into these summaries so this is the better place for the warning. The NULL warning is removed from `StreamChecker` in D137790. Additionally the same problem can happen with `BufferSizeConstraint` at other function summaries, we can say generally (or more often) that if a buffer has size of 0 it is allowed to be NULL pointer.
Aha, okay, so we should extend the existing infrastructure to express this as well. Please do that in another patch though! Thanks!


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