[PATCH] D143300: [randstruct] Don't allow implicit forward decl to stop struct randomization

[Bill Wendling via Phabricator via cfe-commits]

void added inline comments.


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Comment at: clang/lib/Sema/SemaDecl.cpp:18891
+        // incomplete definition.
+        if (const auto *RD = dyn_cast<RecordDecl>(D))
+          return !RD->isCompleteDefinition();
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nickdesaulniers wrote:
> nickdesaulniers wrote:
> > void wrote:
> > > nickdesaulniers wrote:
> > > > what about `EnumDecl`s? I suspect the shared common base `TagDecl` might be better to use?
> > > > 
> > > > If it is, can you add a test?  I'm guessing
> > > > 
> > > > ```
> > > > struct foo {
> > > >   enum havent_seen_yet;
> > > >   enum havent_seen_yet2;
> > > > }
> > > > ```
> > > > would be the test case.
> > > Would testing for a `TagDecl` be better here?
> > I think so; common shared base and same logic for both cases here.  Unless there's something other than RecordDecl and EnumDecl where this shouldn't apply.
> > Unless there's something other than RecordDecl and EnumDecl where this shouldn't apply.
> 
> The `TagDecl` constructor is only called from the `RecordDecl` and `EnumDecl` constructors.  So I think it's simpler to just check `TagDecl` base type rather than each of the two derived types.
I like that better. Done. :)


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Comment at: clang/test/CodeGen/init-randomized-struct-fwd-decl.c:2
+// RUN: %clang_cc1 -triple=x86_64-unknown-linux -emit-llvm -frandomize-layout-seed=1234567890abcdef < %s | FileCheck %s
+// RUN: %clang_cc1 -triple=x86_64-unknown-linux -emit-llvm -frandomize-layout-seed=1234567890abcdef -DFORWARD_DECL < %s | FileCheck -check-prefix=FWD-DECL %s
+// PR60349
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nickdesaulniers wrote:
> Is the second check prefix necessary? The check lines look the same to me, unless I'm missing something.
> 
> Removing it should let us also drop the redundant FWD-DECL lines below.
It's there to check that the randomization doesn't change if the forward decl is outside of the structure. However, Windows yet again uses a different algorithm than Linux and generates a different randomized ordering. It's annoying. I can remove this check.


Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D143300/new/

https://reviews.llvm.org/D143300