[PATCH] Disabling of "redefine_extname" pragma for C++ code

[Aaron Ballman]

On Mon, Jun 29, 2015 at 11:13 AM, Andrey Bokhanko
<andreybokhanko at gmail.com> wrote:
> Hi aaron.ballman, rsmith,
>
> In response to Richard Smith's comment (http://lists.cs.uiuc.edu/pipermail/cfe-commits/Week-of-Mon-20150622/131782.html), this patch disables "redefine_extname" pragma for C++ code. Also, I added a test that this pragma doesn't apply to static declarations.
>
> http://reviews.llvm.org/D10805
>
> Files:
>   lib/Sema/SemaDecl.cpp
>   test/CodeGen/redefine_extname.c
>   test/CodeGenCXX/redefine_extname.cpp
>
> Index: test/CodeGenCXX/redefine_extname.cpp
> ===================================================================
> --- test/CodeGenCXX/redefine_extname.cpp
> +++ test/CodeGenCXX/redefine_extname.cpp
> @@ -28,3 +28,9 @@
>  // CHECK: define i32 @bar()
>  }
>
> +// Check that pragma redefine_extname applies to C code only, and shouldn't be
> +// applied to C++.
> +#pragma redefine_extname foo_cpp bar_cpp
> +extern int foo_cpp() { return 1; }
> +// CHECK-NOT: define i32 @bar_cpp()
> +
> Index: test/CodeGen/redefine_extname.c
> ===================================================================
> --- test/CodeGen/redefine_extname.c
> +++ test/CodeGen/redefine_extname.c
> @@ -24,3 +24,9 @@
>  extern int foo() { return 1; }
>  // CHECK: define i32 @bar()
>
> +// Check that pragma redefine_extname applies to external declarations only.
> +#pragma redefine_extname foo_static bar_static
> +static int foo_static() { return 1; }
> +int baz() { return foo_static(); }
> +// CHECK-NOT: call i32 @bar_static()

Since this is becoming more and more specific behavior, should this
warn when there are *no* declarations renamed, but there are
declarations with the same name? I can see wasting a lot of time
trying to debug the above test case.

> +
> Index: lib/Sema/SemaDecl.cpp
> ===================================================================
> --- lib/Sema/SemaDecl.cpp
> +++ lib/Sema/SemaDecl.cpp
> @@ -5525,15 +5525,16 @@
>    return true;
>  }
>
> -/// \brief Returns true if given declaration is TU-scoped and externally
> -/// visible.
> -static bool isDeclTUScopedExternallyVisible(const Decl *D) {
> +/// \brief Returns true if given declaration has external C language linkage.
> +static bool isDeclExternC(const Decl *D) {
>    if (auto *FD = dyn_cast<FunctionDecl>(D))
> -    return (FD->getDeclContext()->isTranslationUnit() || FD->isExternC()) &&
> -           FD->hasExternalFormalLinkage();
> +  {
> +    return FD->isExternC();
> +  }

Braces go with the if, not on a new line.

>    else if (auto *VD = dyn_cast<VarDecl>(D))
> -    return (VD->getDeclContext()->isTranslationUnit() || VD->isExternC()) &&
> -           VD->hasExternalFormalLinkage();
> +  {
> +    return VD->isExternC();
> +  }

Same here.

>
>    llvm_unreachable("Unknown type of decl!");
>  }
> @@ -5963,7 +5964,7 @@
>      NewVD->addAttr(::new (Context) AsmLabelAttr(SE->getStrTokenLoc(0),
>                                                  Context, Label, 0));
>    } else if (!ExtnameUndeclaredIdentifiers.empty() &&
> -             isDeclTUScopedExternallyVisible(NewVD)) {
> +             isDeclExternC(NewVD)) {
>      llvm::DenseMap<IdentifierInfo*,AsmLabelAttr*>::iterator I =
>        ExtnameUndeclaredIdentifiers.find(NewVD->getIdentifier());
>      if (I != ExtnameUndeclaredIdentifiers.end()) {
> @@ -7491,7 +7492,7 @@
>      NewFD->addAttr(::new (Context) AsmLabelAttr(SE->getStrTokenLoc(0), Context,
>                                                  SE->getString(), 0));
>    } else if (!ExtnameUndeclaredIdentifiers.empty() &&
> -             isDeclTUScopedExternallyVisible(NewFD)) {
> +             isDeclExternC(NewFD)) {
>      llvm::DenseMap<IdentifierInfo*,AsmLabelAttr*>::iterator I =
>        ExtnameUndeclaredIdentifiers.find(NewFD->getIdentifier());
>      if (I != ExtnameUndeclaredIdentifiers.end()) {
> @@ -14284,7 +14285,7 @@
>    // already exists, add a label attribute to it.
>    if (PrevDecl &&
>        (isa<FunctionDecl>(PrevDecl) || isa<VarDecl>(PrevDecl)) &&
> -      PrevDecl->hasExternalFormalLinkage())
> +      isDeclExternC(PrevDecl))
>      PrevDecl->addAttr(Attr);
>    // Otherwise, add a label atttibute to ExtnameUndeclaredIdentifiers.
>    else

~Aaron

>
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