[DPDK/core Bug 1425] enable_stdatomic=true breaks C++ on GCC 11 and earlier

[Mattias Rönnblom]

On 2024-04-30 01:14, Tyler Retzlaff wrote:
> On Mon, Apr 29, 2024 at 06:21:13AM +0000, bugzilla at dpdk.org wrote:
>> https://bugs.dpdk.org/show_bug.cgi?id=1425
>>
>>              Bug ID: 1425
>>             Summary: enable_stdatomic=true breaks C++  on GCC 11 and
>>                      earlier
>>             Product: DPDK
>>             Version: 23.11
>>            Hardware: All
>>                  OS: Linux
>>              Status: UNCONFIRMED
>>            Severity: normal
>>            Priority: Normal
>>           Component: core
>>            Assignee: dev at dpdk.org
>>            Reporter: mattias.ronnblom at ericsson.com
>>    Target Milestone: ---
>>
>> On GCC 11 and earlier, configuring enable_stdatomic=true prevents the use of
>> all DPDK header files that directly or indirectly include <rte_stdatomic.h>
>> from a C++ translation unit (e.g., app).
>>
>> <rte_stdatomic.h> includes <stdatomic.h>, which in turn is not necessarily
>> C++-compatible.
> 
> This is known but to add some information.
> 

Is it also documented?

> C++ and enable_stdatomic=true for llvm and gcc are not currently
> supported. the combination will remain unsupported for C++ compilers
> that do not support -std=c++23 which is the first C++ standard that
> requires interoperability with C11 stdatomic.h >
> When enable_stdatomic=true there are bugs/incorrect usages of atomic
> qualifier in casts that (even when using C++23) cause compilation
> failure. These are a fixable but are low priority without -std=c++23.
> 
> Finally, the legacy atomics remain unconverted to stdatomic. This will
> cause enable_stdatomic=true not to build when using llvm (but not gcc)
> because llvm strictly enforces qualification when using atomic generics.
>

OK, I see. It'll be a while until enable_stdatomic is usable outside 
Windows then, for generic builds.

Am I right if I say that C++23-capable compilers/run-times are supposed 
to have a <stdatomic.h> which interoperates with C++ even in C++11-mode? 
Or need the application be compiled as C++23.

>>
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