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Re: Does gcc conform to C++ ABI?
On Fri, Feb 13, 2009 at 11:05 AM, Ian Lance Taylor <iant@google.com> wrote:
> "H.J. Lu" <hjl.tools@gmail.com> writes:
>
>> It may be a known issue. Does gcc follow Section 5.1.6 Scope Encoding
>> in C++ ABI:
>>
>> http://www.codesourcery.com/public/cxx-abi/abi.html#mangling
>>
>> I tried the example. But it won't compile. I changed it to:
>>
>> [hjl@gnu-6 tmp]$ cat x.cc
>> namespace N {
>> inline char f(int i) {
>> static const char *p = "Itanium C++ ABI"; // p = 1, "..." = 2
>> { struct X { // X = 3
>> void g() {}
>> }; }
>> return p[i];
>> }
>> char
>> foo (int i)
>> {
>> return f (i);
>> }
>> }
>> [hjl@gnu-6 tmp]$ gcc -c x.cc
>> [hjl@gnu-6 tmp]$ nm x.o
>> 0000000000000000 W _ZN1N1fEi
>> 0000000000000000 T _ZN1N3fooEi
>> 0000000000000000 V _ZZN1N1fEiE1p
>> U __gxx_personality_v0
>> [hjl@gnu-6 tmp]$ nm x.o | c++filt
>> 0000000000000000 W N::f(int)
>> 0000000000000000 T N::foo(int)
>> 0000000000000000 V N::f(int)::p
>> U __gxx_personality_v0
>> [hjl@gnu-6 tmp]$
>>
>> It doesn't
>>
>> "_ZZN1N1fEiEs": encoding of N::f::"Itanium C++ ABI" (no discriminator)
>
> The discriminator is optional and is up to the discretion of the
> compiler. This doesn't matter for interoperability purposes, because
> such names can not be referenced from other translation units anyhow.
If it isn't optional, tools can't depend on it. I was wondering
how useful it was.
Another issue for scope encoding. C++ ABI:
---
Occasionally entities in local scopes must be mangled too
(e.g. because inlining or template compilation causes multiple
translation units to require access to that entity).
---
seems to imply that the local symbols may have external
linkage. Am I wrong?
> What do you think the symbol name should be?
>
Isn't it specified in C++ ABI?
--
H.J.