Re: [PATCH] Fix gnu-versioned-namespace build

[Jonathan Wakely <jwakely@redhat.com>]

On 11/12/19 22:28 +0100, François Dumont wrote:
>On 12/11/19 9:44 PM, Jonathan Wakely wrote:
>>On 11/12/19 21:23 +0100, François Dumont wrote:
>>>On 12/11/19 12:16 PM, Jonathan Wakely wrote:
>>>>On 11/12/19 08:29 +0100, François Dumont wrote:
>>>>>I plan to commit this tomorrow.
>>>>>
>>>>>Note that rather than just adding the missing 
>>>>>_GLIBCXX_[BEGIN,END]_VERSION_NAMESPACE I also move anonymous 
>>>>>namespace usage outside std namespace. Let me know if it was 
>>>>>intentional.
>>>>
>>>>It was intentional, why move it?
>>>
>>>I just don't get the intention so I proposed to move it. But there 
>>>are indeed other usages of this pattern in other src files.
>>>
>>>Note that in src/c++11/debug.cc I am using anonymous namespace at 
>>>global scope, is that wrong ?
>>
>>It's certainly more fragile, so arguably it's wrong, yes.
>>
>>Consider:
>>
>>// some libc function in a system header we don't control:
>>extern "C" void __foo();
>>
>>// libstdc++ code in a .cc file:
>>namespace
>>{
>> void foo() { }
>>}
>>namespace std
>>{
>> void bar() { foo(); }
>>}
>>
>>This fails to compile, because the name foo is ambiguous in the global
>>scope. We don't control the libc headers, so we don't know all the
>>names they might declare at global scope.
>>
>>If you don't put the unnamed namespace at global scope, the problem
>>simply doesn't exist:
>>
>>namespace std
>>{
>> namespace
>> {
>>   void foo() { }
>> }
>>
>> void bar() { foo(); }
>>}
>>
>>Now it doesn't matter what names libc puts in the global scope,
>>because we're never looking for foo in the global scope.
>>
>>It's obviously better to add our declarations to our own namespace
>>that we control, not to the global namespace (and an unnamed namespace
>>at global scope effectively adds the names to the global namespace).
>>
>>>>
>>>>Adding the BEGIN/END_VERSION macros is unnecessary. Those namespaces
>>>>are inline, so std::random_device already refers to
>>>>std::__8::random_device when the original declaration was in the
>>>>versioned namespace.
>>>
>>>Ok. I must confess I wasn't clear about this but looking at other 
>>>src files, at least in src/c++11, was showing that it is done 
>>>almost always this way, I guess we could cleanup those files.
>>>
>>>>
>>>>The only fix needed here seems to be qualifying std::isdigit (and
>>>>strictly-speaking we should also include <cctype> to declare that).
>>>>
>>>Like in attached patch ?
>>
>>Did you attach the wrong patch?
>>
>>
>Indeed, here is the correct one.

OK for trunk (including <cctype> unconditionally is fine).
Thanks.


>

>diff --git a/libstdc++-v3/src/c++11/random.cc b/libstdc++-v3/src/c++11/random.cc
>index 10fbe1dc4c4..04edc582b69 100644
>--- a/libstdc++-v3/src/c++11/random.cc
>+++ b/libstdc++-v3/src/c++11/random.cc
>@@ -41,6 +41,7 @@
> 
> #include <cerrno>
> #include <cstdio>
>+#include <cctype> // For std::isdigit.
> 
> #if defined _GLIBCXX_HAVE_UNISTD_H && defined _GLIBCXX_HAVE_FCNTL_H
> # include <unistd.h>
>@@ -286,7 +287,7 @@ namespace std _GLIBCXX_VISIBILITY(default)
>     _M_mt.seed(seed);
> #else
>     // Convert old default token "mt19937" or numeric seed tokens to "default".
>-    if (token == "mt19937" || isdigit((unsigned char)token[0]))
>+    if (token == "mt19937" || std::isdigit((unsigned char)token[0]))
>       _M_init("default");
>     else
>       _M_init(token);