r349201 - Add extension to always default-initialize nullptr_t.
Richard Smith via cfe-commits
cfe-commits at lists.llvm.org
Fri Dec 14 14:55:09 PST 2018
Attached. With the functional part of your change reverted and this
applied, the modified tests still pass except
error: 'note' diagnostics expected but not seen:
File
/usr/local/google/home/richardsmith/llvm-git-1/src/tools/clang/test/Analysis/nullptr.cpp
Line 128: 'p' initialized to a null pointer value
error: 'note' diagnostics seen but not expected:
File
/usr/local/google/home/richardsmith/llvm-git-1/src/tools/clang/test/Analysis/nullptr.cpp
Line 128: 'p' declared without an initial value
... which seems accurate (but perhaps not useful).
On Fri, 14 Dec 2018 at 14:47, Richard Smith <richard at metafoo.co.uk> wrote:
> I have a patch I put together a while back as an attempt to fix a
> different bug, that creates a new CastKind for this operation (didn't work
> out there, but it might do so here). I'll dig it out and mail it to you in
> case it's a useful starting point.
>
> On Fri, 14 Dec 2018 at 14:42, Keane, Erich via cfe-commits <
> cfe-commits at lists.llvm.org> wrote:
>
>> Alright, no problem. I’ll push a revert in a few minutes and give it
>> another try. Perhaps I can suppress the creation of a CK_LValueToRValue in
>> the case where it’s a read from nullptr_t
>>
>>
>>
>>
>>
>> *From:* Richard Smith [mailto:richard at metafoo.co.uk]
>> *Sent:* Friday, December 14, 2018 2:41 PM
>> *To:* Keane, Erich <erich.keane at intel.com>
>> *Cc:* cfe-commits <cfe-commits at lists.llvm.org>
>> *Subject:* Re: r349201 - Add extension to always default-initialize
>> nullptr_t.
>>
>>
>>
>> Sorry, I was late with my review comment. I think this is the wrong way
>> to approach this problem. This does not "fix all situations where nullptr_t
>> would seem uninitialized", and it makes our AST representation lose source
>> fidelity.
>>
>>
>>
>> On Fri, 14 Dec 2018 at 14:25, Erich Keane via cfe-commits <
>> cfe-commits at lists.llvm.org> wrote:
>>
>> Author: erichkeane
>> Date: Fri Dec 14 14:22:29 2018
>> New Revision: 349201
>>
>> URL: http://llvm.org/viewvc/llvm-project?rev=349201&view=rev
>> Log:
>> Add extension to always default-initialize nullptr_t.
>>
>> Core issue 1013 suggests that having an uninitialied std::nullptr_t be
>> UB is a bit foolish, since there is only a single valid value. This DR
>> reports that DR616 fixes it, which does so by making lvalue-to-rvalue
>> conversions from nullptr_t be equal to nullptr.
>>
>> However, just implementing that results in warnings/etc in many places.
>> In order to fix all situations where nullptr_t would seem uninitialized,
>> this patch instead (as an otherwise transparent extension) default
>> initializes uninitialized VarDecls of nullptr_t.
>>
>> Differential Revision: https://reviews.llvm.org/D53713
>>
>> Change-Id: I84d72a9290054fa55341e8cbdac43c8e7f25b885
>>
>> Added:
>> cfe/trunk/test/SemaCXX/nullptr_t-init.cpp (with props)
>> Modified:
>> cfe/trunk/lib/Sema/SemaInit.cpp
>> cfe/trunk/test/Analysis/nullptr.cpp
>> cfe/trunk/test/SemaCXX/ast-print-crash.cpp
>>
>> Modified: cfe/trunk/lib/Sema/SemaInit.cpp
>> URL:
>> http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/SemaInit.cpp?rev=349201&r1=349200&r2=349201&view=diff
>>
>> ==============================================================================
>> --- cfe/trunk/lib/Sema/SemaInit.cpp (original)
>> +++ cfe/trunk/lib/Sema/SemaInit.cpp Fri Dec 14 14:22:29 2018
>> @@ -4881,6 +4881,13 @@ static void TryDefaultInitialization(Sem
>> return;
>> }
>>
>> + // As an extension, and to fix Core issue 1013, zero initialize
>> nullptr_t.
>> + // Since there is only 1 valid value of nullptr_t, we can just use
>> that.
>> + if (DestType->isNullPtrType()) {
>> + Sequence.AddZeroInitializationStep(Entity.getType());
>> + return;
>> + }
>> +
>> // - otherwise, no initialization is performed.
>>
>> // If a program calls for the default initialization of an object of
>>
>> Modified: cfe/trunk/test/Analysis/nullptr.cpp
>> URL:
>> http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Analysis/nullptr.cpp?rev=349201&r1=349200&r2=349201&view=diff
>>
>> ==============================================================================
>> --- cfe/trunk/test/Analysis/nullptr.cpp (original)
>> +++ cfe/trunk/test/Analysis/nullptr.cpp Fri Dec 14 14:22:29 2018
>> @@ -125,21 +125,16 @@ struct Type {
>> };
>>
>> void shouldNotCrash() {
>> - decltype(nullptr) p; // expected-note{{'p' declared without an initial
>> value}}
>> - if (getSymbol()) // expected-note {{Assuming the condition is false}}
>> - // expected-note at -1{{Taking false branch}}
>> - // expected-note at -2{{Assuming the condition is
>> false}}
>> - // expected-note at -3{{Taking false branch}}
>> - // expected-note at -4{{Assuming the condition is true}}
>> - // expected-note at -5{{Taking true branch}}
>> - invokeF(p); // expected-warning{{1st function call argument is an
>> uninitialized value}}
>> - // expected-note at -1{{1st function call argument is an
>> uninitialized value}}
>> + decltype(nullptr) p; // expected-note{{'p' initialized to a null
>> pointer value}}
>> if (getSymbol()) // expected-note {{Assuming the condition is false}}
>> // expected-note at -1{{Taking false branch}}
>> // expected-note at -2{{Assuming the condition is true}}
>> // expected-note at -3{{Taking true branch}}
>> - invokeF(nullptr); // expected-note {{Calling 'invokeF'}}
>> - // expected-note at -1{{Passing null pointer value
>> via 1st parameter 'x'}}
>> + invokeF(p); // expected-note{{Passing null pointer value via 1st
>> parameter 'x'}}
>> + // expected-note at -1{{Calling 'invokeF'}}
>> + if (getSymbol()) // expected-note {{Assuming the condition is false}}
>> + // expected-note at -1{{Taking false branch}}
>> + invokeF(nullptr);
>> if (getSymbol()) { // expected-note {{Assuming the condition is
>> true}}
>> // expected-note at -1{{Taking true branch}}
>> X *xx = Type().x; // expected-note {{Null pointer value stored to
>> field 'x'}}
>>
>> Modified: cfe/trunk/test/SemaCXX/ast-print-crash.cpp
>> URL:
>> http://llvm.org/viewvc/llvm-project/cfe/trunk/test/SemaCXX/ast-print-crash.cpp?rev=349201&r1=349200&r2=349201&view=diff
>>
>> ==============================================================================
>> --- cfe/trunk/test/SemaCXX/ast-print-crash.cpp (original)
>> +++ cfe/trunk/test/SemaCXX/ast-print-crash.cpp Fri Dec 14 14:22:29 2018
>> @@ -7,6 +7,6 @@
>>
>> // CHECK: struct {
>> // CHECK-NEXT: } dont_crash_on_syntax_error;
>> -// CHECK-NEXT: decltype(nullptr) p;
>> +// CHECK-NEXT: decltype(nullptr) p(/*implicit*/(decltype(nullptr))0);
>> struct {
>> } dont_crash_on_syntax_error /* missing ; */ decltype(nullptr) p;
>>
>> Added: cfe/trunk/test/SemaCXX/nullptr_t-init.cpp
>> URL:
>> http://llvm.org/viewvc/llvm-project/cfe/trunk/test/SemaCXX/nullptr_t-init.cpp?rev=349201&view=auto
>>
>> ==============================================================================
>> --- cfe/trunk/test/SemaCXX/nullptr_t-init.cpp (added)
>> +++ cfe/trunk/test/SemaCXX/nullptr_t-init.cpp Fri Dec 14 14:22:29 2018
>> @@ -0,0 +1,10 @@
>> +// RUN: %clang_cc1 -fsyntax-only -verify -std=c++11 -ffreestanding
>> -Wuninitialized %s
>> +// expected-no-diagnostics
>> +typedef decltype(nullptr) nullptr_t;
>> +
>> +// Ensure no 'uninitialized when used here' warnings (Wuninitialized),
>> for
>> +// nullptr_t always-initialized extension.
>> +nullptr_t default_init() {
>> + nullptr_t a;
>> + return a;
>> +}
>>
>> Propchange: cfe/trunk/test/SemaCXX/nullptr_t-init.cpp
>>
>> ------------------------------------------------------------------------------
>> svn:eol-style = native
>>
>> Propchange: cfe/trunk/test/SemaCXX/nullptr_t-init.cpp
>>
>> ------------------------------------------------------------------------------
>> svn:keywords = "Author Date Id Rev URL"
>>
>> Propchange: cfe/trunk/test/SemaCXX/nullptr_t-init.cpp
>>
>> ------------------------------------------------------------------------------
>> svn:mime-type = text/plain
>>
>>
>> _______________________________________________
>> cfe-commits mailing list
>> cfe-commits at lists.llvm.org
>> http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
>>
>> _______________________________________________
>> cfe-commits mailing list
>> cfe-commits at lists.llvm.org
>> http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
>>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/cfe-commits/attachments/20181214/1475e907/attachment-0001.html>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: nullptr-lval-to-rval.patch
Type: application/octet-stream
Size: 12306 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/cfe-commits/attachments/20181214/1475e907/attachment-0001.obj>
More information about the cfe-commits
mailing list