[PATCH] D19708: [CGDebugInfo] Generate debug info for member calls in the context of the callee expression

[Hal Finkel via cfe-commits]

----- Original Message -----
> From: "David Blaikie" <dblaikie at gmail.com>
> To: reviews+D19708+public+e9ddc425037326c5 at reviews.llvm.org, "Hal Finkel" <hfinkel at anl.gov>
> Cc: "Richard Smith" <richard at metafoo.co.uk>, "Adrian Prantl" <aprantl at apple.com>, "Duncan P. N. Exon Smith"
> <dexonsmith at apple.com>, "Eric Christopher" <echristo at gmail.com>, "Jun Bum Lim" <junbuml at codeaurora.org>,
> "cfe-commits" <cfe-commits at lists.llvm.org>
> Sent: Friday, April 29, 2016 4:52:26 PM
> Subject: Re: [PATCH] D19708: [CGDebugInfo] Generate debug info for member calls in the context of the callee
> expression
> 
> 
> You could simplify the test case further, down to just:
> 
> struct foo { void bar(); };
> void f(foo *f) {
> f->bar();
> }
> 
> and check that the call instruction has the desired column (or if you
> want a test that doesn't depend on column info (you can force it on
> with a flag, but we might vary whether it's on by default based on
> target, etc, I'm not sure) you could put 'bar();' on a separate line
> from 'f->' and check the call was on the second line and not the
> first).

Certainly. I'm not sure much we want to reduce the test case, however, because I particularly want to cover the case of two calls on the same line with column info. Given that this is still pretty simple, I think that covering it directly seems reasonable.

> 
> Richard might be able to tell us whether there's a preferred place
> for a test for a change like this - should it be a debug info test,
> a diagnostic test,

At least for the test you suggested in a previous e-mail, this patch has no effect on the output diagnostics (although it certainly does have the desired effect on the debug info). Specifically, even with this patch, we still have:

  $ cat /tmp/loc.cpp 
  struct foo {
    const foo *x() const;
    void y();
  };
  
  void f(const foo *g) {
    g->x()->y();
    g->x()->x()->y();
  }

$ clang /tmp/loc.cpp -fsyntax-only
  /tmp/loc.cpp:7:3: error: member function 'y' not viable: 'this' argument has type 'const foo', but function is not marked const
    g->x()->y();
    ^~~~~~
  /tmp/loc.cpp:3:8: note: 'y' declared here
    void y();
         ^
  /tmp/loc.cpp:8:3: error: member function 'y' not viable: 'this' argument has type 'const foo', but function is not marked const
    g->x()->x()->y();
    ^~~~~~~~~~~
  /tmp/loc.cpp:3:8: note: 'y' declared here
    void y();
         ^
  2 errors generated.

Thanks again,
Hal

> or perhaps just an ast dump test?
> 
> Perhaps a test for the case where there is no valid callee would be
> good? Where does that come up - call through a member function
> pointer?
> 
> 
> On Fri, Apr 29, 2016 at 9:19 AM, Hal Finkel via cfe-commits <
> cfe-commits at lists.llvm.org > wrote:
> 
> 
> hfinkel updated this revision to Diff 55610.
> hfinkel added a comment.
> 
> Use David's suggested approach: Modify the preferred expression
> location for member calls. If the callee has a valid location (not
> all do), then use that. Otherwise, fall back to the starting
> location. This seems to cleanly fix the debug-info problem.
> 
> 
> http://reviews.llvm.org/D19708
> 
> Files:
> include/clang/AST/ExprCXX.h
> 
> 
> test/CodeGenCXX/debug-info-member-call.cpp
> 
> Index: test/CodeGenCXX/debug-info-member-call.cpp
> ===================================================================
> --- /dev/null
> +++ test/CodeGenCXX/debug-info-member-call.cpp
> @@ -0,0 +1,24 @@
> +// RUN: %clang_cc1 -triple x86_64-unknown_unknown -emit-llvm
> -debug-info-kind=standalone -dwarf-column-info %s -o - | FileCheck
> %s
> +void ext();
> +
> +struct Bar {
> + void bar() { ext(); }
> +};
> +
> +struct Foo {
> + Bar *b;
> +
> + Bar *foo() { return b; }
> +};
> +
> +void test(Foo *f) {
> + f->foo()->bar();
> +}
> +
> +// CHECK-LABEL: @_Z4testP3Foo
> +// CHECK: call {{.*}} @_ZN3Foo3fooEv{{.*}}, !dbg ![[CALL1LOC:.*]]
> +// CHECK: call void @_ZN3Bar3barEv{{.*}}, !dbg ![[CALL2LOC:.*]]
> +
> +// CHECK: ![[CALL1LOC]] = !DILocation(line: [[LINE:[0-9]+]], column:
> 6,
> +// CHECK: ![[CALL2LOC]] = !DILocation(line: [[LINE]], column: 13,
> +
> Index: include/clang/AST/ExprCXX.h
> ===================================================================
> --- include/clang/AST/ExprCXX.h
> +++ include/clang/AST/ExprCXX.h
> @@ -145,6 +145,14 @@
> /// FIXME: Returns 0 for member pointer call exprs.
> CXXRecordDecl *getRecordDecl() const;
> 
> + SourceLocation getExprLoc() const LLVM_READONLY {
> + SourceLocation CLoc = getCallee()->getExprLoc();
> + if (CLoc.isValid())
> + return CLoc;
> +
> + return getLocStart();
> + }
> +
> static bool classof(const Stmt *T) {
> return T->getStmtClass() == CXXMemberCallExprClass;
> }
> 
> 
> 
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> 

-- 
Hal Finkel
Assistant Computational Scientist
Leadership Computing Facility
Argonne National Laboratory