On Wed, Aug 23, 2023 at 04:23:00PM -0400, Jason Merrill wrote:
> I'd be surprised if this would affect any real code, but I suppose so. In
> any case I'd like to fix this at the same time as the local statics, to
> avoid changing their mangled name twice.
Ok.
Running now into a problem with abi tags, because cp_maybe_mangle_decomp
is called before the type of the structured binding is finalized (sequence
is cp_maybe_mangle_decomp; cp_finish_decl; cp_finish_decomp), I vaguely
remember the reason was to have the name already mangled by cp_finish_decl
time, so that it can add it into varpool etc..
Will see if I can e.g. pass the initializer expression to
cp_maybe_mangle_decomp and figure out the tags from that.
> > @@ -9049,6 +9050,25 @@ cp_maybe_mangle_decomp (tree decl, tree
> > tree d = first;
> > for (unsigned int i = 0; i < count; i++, d = DECL_CHAIN (d))
> > v[count - i - 1] = d;
> > + if (DECL_FUNCTION_SCOPE_P (decl))
> > + {
> > + size_t sz = 3;
> > + for (unsigned int i = 0; i < count; ++i)
> > + sz += IDENTIFIER_LENGTH (DECL_NAME (v[i])) + 1;
> > + char *name = XALLOCAVEC (char, sz);
> > + name[0] = 'D';
> > + name[1] = 'C';
> > + char *p = name + 2;
> > + for (unsigned int i = 0; i < count; ++i)
> > + {
> > + size_t len = IDENTIFIER_LENGTH (DECL_NAME (v[i]));
> > + *p++ = ' ';
> > + memcpy (p, IDENTIFIER_POINTER (DECL_NAME (v[i])), len);
> > + p += len;
> > + }
> > + *p = '\0';
> > + determine_local_discriminator (decl, get_identifier (name));
> > + }
>
> Maybe do this in mangle_decomp, based on the actual mangling in process
> instead of this pseudo-mangling?
Not sure that is possible, for 2 reasons:
1) determine_local_discriminator otherwise works on DECL_NAME, not mangled
names, so if one uses (albeit implementation reserved)
_ZZN1N3fooI1TB3bazEEivEDC1h1iEB6foobar and similar identifiers, they
could clash with the counting of the structured bindings
2) seems the local discriminator counting shouldn't take into account
details like abi tags, e.g. if I have:
struct [[gnu::abi_tag ("foobar")]] S { int a; };
namespace N {
template <typename T>
inline int
foo ()
{
static int h = 42; int r = ++h;
{ static S h = { 42 }; r += ++h.a; }
{ static int h = 42; r += ++h; }
{ static S h = { 42 }; r += ++h.a; }
return r;
}
}
int (*p) () = N::foo<int>;
then both GCC and Clang mangle these as
_ZZN1N3fooIiEEivE1h
_ZZN1N3fooIiEEivE1hB6foobar_0
_ZZN1N3fooIiEEivE1h_1
_ZZN1N3fooIiEEivE1hB6foobar_2
so whether abi tags appear in the mangled name or not shouldn't result
in separate buckets for counting.
>
> > @@ -4564,6 +4519,13 @@ write_guarded_var_name (const tree varia
> > /* The name of a guard variable for a reference temporary should refer
> > to the reference, not the temporary. */
> > write_string (IDENTIFIER_POINTER (DECL_NAME (variable)) + 4);
> > + else if (DECL_DECOMPOSITION_P (variable)
> > + && DECL_NAME (variable) == NULL_TREE
> > + && startswith (IDENTIFIER_POINTER (DECL_ASSEMBLER_NAME (variable)),
> > + "_Z"))
>
> Maybe add a startswith overload that takes an identifier?
Ok.
> > @@ -4630,7 +4592,10 @@ mangle_ref_init_variable (const tree var
> > start_mangling (variable);
> > write_string ("_ZGR");
> > check_abi_tags (variable);
> > - write_name (variable, /*ignore_local_scope=*/0);
> > + if (DECL_DECOMPOSITION_P (variable))
> > + write_guarded_var_name (variable);
> > + else
> > + write_name (variable, /*ignore_local_scope=*/0);
>
> Why not use write_guarded_name unconditionally?
Ok.
Jakub
