[PATCH] Make __PRETTY_FUNCTION__-like functions mergeable string csts (PR c++/64266).

[Jason Merrill]

On Fri, Oct 26, 2018 at 3:14 AM Martin Liška <mliska@suse.cz> wrote:
> On 10/24/18 7:24 PM, Jason Merrill wrote:
> > On Tue, Oct 23, 2018 at 4:59 AM Martin Liška <mliska@suse.cz> wrote:
> >> However, I still see some minor ICEs, it's probably related to decay_conversion in cp_fname_init:
> >>
> >> 1) ./xg++ -B. /home/marxin/Programming/gcc/gcc/testsuite/g++.dg/cpp0x/lambda/lambda-__func__2.C
> >>
> >> /home/marxin/Programming/gcc/gcc/testsuite/g++.dg/cpp0x/lambda/lambda-__func__2.C:6:17: internal compiler error: Segmentation fault
> >> 6 |     [] { return __func__; }();
> >>   |                 ^~~~~~~~
> >> 0x1344568 crash_signal
> >>         /home/marxin/Programming/gcc/gcc/toplev.c:325
> >> 0x7ffff6bc310f ???
> >>         /usr/src/debug/glibc-2.27-6.1.x86_64/signal/../sysdeps/unix/sysv/linux/x86_64/sigaction.c:0
> >> 0x9db134 is_capture_proxy(tree_node*)
>
> Hi.
>
> >
> > The problem in both tests is that is_capture_proxy thinks your
> > __func__ VAR_DECL with DECL_VALUE_EXPR is a capture proxy, since it is
> > neither an anonymous union proxy nor a structured binding.
>
> I see, however I'm a rookie in area of C++ FE. Would it be solvable this problem
> with lambdas?
>
> >
> > The standard says,
> >
> > The function-local predefined variable __func__ is defined as if a
> > definition of the form
> >    static const char __func__[] = "function-name ";
> > had been provided, where function-name is an implementation-defined
> > string. It is unspecified whether such a variable has an address
> > distinct from that of any other object in the program.
> >
> > So changing the type of __func__ (from array to pointer) still breaks
> > conformance.  And we need to keep the type checks from pretty4.C, even
> > though the checks for strings being distinct need to go.
>
> I added following patch which puts back type to const char[] (instead of char *)
> and I made the variable static. Now I see pretty4.C testcase passing again.
> To be honest I'm not convinced about the FE changes, so a help would
> be appreciated.

OK, I'll poke at it.

Jason