r255371 - Error on redeclaring with a conflicting asm label and on redeclaring with an asm label after the first ODR-use. Detects problems like the one in PR22830 where gcc and clang both compiled the file but with different behaviour.
Kostya Serebryany via cfe-commits
cfe-commits at lists.llvm.org
Mon Jan 4 15:39:37 PST 2016
Thanks for checking, Nick!
+Roland, FYI (recent changes in clang break compilation of all of the
glibc),
similar to https://llvm.org/bugs/show_bug.cgi?id=22830#c1
On Mon, Jan 4, 2016 at 3:21 PM, Nick Lewycky <nicholas at mxc.ca> wrote:
> On 01/04/2016 01:40 PM, Kostya Serebryany wrote:
>
>>
>>
>> On Thu, Dec 17, 2015 at 5:03 PM, Richard Smith <richard at metafoo.co.uk
>> <mailto:richard at metafoo.co.uk>> wrote:
>>
>> On Thu, Dec 17, 2015 at 3:59 PM, Nick Lewycky via cfe-commits
>> <cfe-commits at lists.llvm.org <mailto:cfe-commits at lists.llvm.org>>
>> wrote:
>>
>> On 12/17/2015 10:47 AM, Kostya Serebryany wrote:
>>
>> I am now observing this error message when building glibc
>> with clang
>> (from trunk):
>> ../include/string.h:101:28: error: cannot apply asm label to
>> function
>> after its first use
>> libc_hidden_builtin_proto (memcpy)
>> (many more instances)
>>
>>
>> Do you think this is a bug in glibc code, or the error
>> message could be
>> more relaxed?
>>
>>
>> Could you email me a .i copy of a failing build? That will help
>> me decide whether it's a bug in the error or in glibc.
>>
>>
>> [sorry for delay,]
>> here is the preprocessed source file from glibc:
>> % clang ~/tmp/a.i 2>&1 | grep error:
>> ../include/sys/stat.h:16:28: error: cannot apply asm label to function
>> after its first use
>> ../include/sys/stat.h:17:30: error: cannot apply asm label to function
>> after its first use
>> ../include/sys/stat.h:18:28: error: cannot apply asm label to function
>> after its first use
>> ../include/sys/stat.h:19:30: error: cannot apply asm label to function
>> after its first use
>> ...
>>
>>
>> Also PR22830 comment 1 seems relevant here.
>>
>>
>> Probably, but since this is a very recent regression in clang I thought
>> I should report it.
>>
>
> This looks like it's WAI:
>
> 3783 extern int __fxstat (int __ver, int __fildes, struct stat
> *__stat_buf)
> 3784 __attribute__ ((__nothrow__ )) ;
> ...
> 3827 extern __inline int
> 3828 __attribute__ ((__nothrow__ )) fstat (int __fd, struct stat
> *__statbuf)
> 3829 {
> 3830 return __fxstat (1, __fd, __statbuf);
> 3831 }
> ...
> 3910 extern __typeof (__fxstat) __fxstat __asm__ ("" "__GI___fxstat")
> __attribute__ ((visibility ("hidden")));
>
> This is exactly the situation where GCC and Clang will emit a different .o
> file.
>
> Nick
>
> On Fri, Dec 11, 2015 at 1:28 PM, Nick Lewycky via cfe-commits
>> <cfe-commits at lists.llvm.org
>> <mailto:cfe-commits at lists.llvm.org>
>> <mailto:cfe-commits at lists.llvm.org
>>
>> <mailto:cfe-commits at lists.llvm.org>>> wrote:
>>
>> Author: nicholas
>> Date: Fri Dec 11 15:28:55 2015
>> New Revision: 255371
>>
>> URL:
>> http://llvm.org/viewvc/llvm-project?rev=255371&view=rev
>> Log:
>> Error on redeclaring with a conflicting asm label and
>> on redeclaring
>> with an asm label after the first ODR-use. Detects
>> problems like the
>> one in PR22830 where gcc and clang both compiled the
>> file but with
>> different behaviour.
>>
>> Added:
>> cfe/trunk/test/Sema/asm-label.c
>> Modified:
>> cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td
>> cfe/trunk/lib/Sema/SemaDecl.cpp
>>
>> Modified:
>> cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td
>> URL:
>>
>> http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td?rev=255371&r1=255370&r2=255371&view=diff
>>
>>
>> ==============================================================================
>> ---
>> cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td
>> (original)
>> +++
>> cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td Fri Dec
>> 11
>> 15:28:55 2015
>> @@ -4259,6 +4259,9 @@ def err_tag_definition_of_typedef
>> : Erro
>> def err_conflicting_types : Error<"conflicting types
>> for %0">;
>> def err_different_pass_object_size_params : Error<
>> "conflicting pass_object_size attributes on
>> parameters">;
>> +def err_late_asm_label_name : Error<
>> + "cannot apply asm label to
>> %select{variable|function}0 after its
>> first use">;
>> +def err_different_asm_label : Error<"conflicting asm
>> label">;
>> def err_nested_redefinition : Error<"nested
>> redefinition of %0">;
>> def err_use_with_wrong_tag : Error<
>> "use of %0 with tag type that does not match
>> previous declaration">;
>>
>> Modified: cfe/trunk/lib/Sema/SemaDecl.cpp
>> URL:
>>
>> http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/SemaDecl.cpp?rev=255371&r1=255370&r2=255371&view=diff
>>
>>
>> ==============================================================================
>> --- cfe/trunk/lib/Sema/SemaDecl.cpp (original)
>> +++ cfe/trunk/lib/Sema/SemaDecl.cpp Fri Dec 11 15:28:55
>> 2015
>> @@ -2379,9 +2379,24 @@ void
>> Sema::mergeDeclAttributes(NamedDecl
>> if (!Old->hasAttrs() && !New->hasAttrs())
>> return;
>>
>> - // attributes declared post-definition are currently
>> ignored
>> + // Attributes declared post-definition are currently
>> ignored.
>> checkNewAttributesAfterDef(*this, New, Old);
>>
>> + if (AsmLabelAttr *NewA =
>> New->getAttr<AsmLabelAttr>()) {
>> + if (AsmLabelAttr *OldA =
>> Old->getAttr<AsmLabelAttr>()) {
>> + if (OldA->getLabel() != NewA->getLabel()) {
>> + // This redeclaration changes __asm__ label.
>> + Diag(New->getLocation(),
>> diag::err_different_asm_label);
>> + Diag(OldA->getLocation(),
>> diag::note_previous_declaration);
>> + }
>> + } else if (Old->isUsed()) {
>> + // This redeclaration adds an __asm__ label to a
>> declaration
>> that has
>> + // already been ODR-used.
>> + Diag(New->getLocation(),
>> diag::err_late_asm_label_name)
>> + << isa<FunctionDecl>(Old) <<
>> New->getAttr<AsmLabelAttr>()->getRange();
>> + }
>> + }
>> +
>> if (!Old->hasAttrs())
>> return;
>>
>>
>> Added: cfe/trunk/test/Sema/asm-label.c
>> URL:
>>
>> http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Sema/asm-label.c?rev=255371&view=auto
>>
>>
>> ==============================================================================
>> --- cfe/trunk/test/Sema/asm-label.c (added)
>> +++ cfe/trunk/test/Sema/asm-label.c Fri Dec 11 15:28:55
>> 2015
>> @@ -0,0 +1,30 @@
>> +// RUN: %clang_cc1 -verify %s
>> +
>> +void f();
>> +void f() __asm__("fish");
>> +void g();
>> +
>> +void f() {
>> + g();
>> +}
>> +void g() __asm__("gold"); // expected-error{{cannot
>> apply asm
>> label to function after its first use}}
>> +
>> +void h() __asm__("hose"); // expected-note{{previous
>> declaration
>> is here}}
>> +void h() __asm__("hair"); //
>> expected-error{{conflicting asm label}}
>> +
>> +int x;
>> +int x __asm__("xenon");
>> +int y;
>> +
>> +int test() { return y; }
>> +
>> +int y __asm__("yacht"); // expected-error{{cannot
>> apply asm label
>> to variable after its first use}}
>> +
>> +int z __asm__("zebra"); // expected-note{{previous
>> declaration is
>> here}}
>> +int z __asm__("zooms"); //
>> expected-error{{conflicting asm label}}
>> +
>> +
>> +// No diagnostics on the following.
>> +void __real_readlink() __asm("readlink");
>> +void readlink() __asm("__protected_readlink");
>> +void readlink() { __real_readlink(); }
>>
>>
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