C++ Features Banned By Google

[Gregor Mückl]

On Saturday, 24 January 2026 at 17:39:21 UTC, H. S. Teoh wrote:
> On Sat, Jan 24, 2026 at 09:29:06AM -0800, Walter Bright via 
> Digitalmars-d wrote:
>> On 1/23/2026 3:58 PM, H. S. Teoh wrote:
>> > Rationale seems to be inadequate support in Clang and GN 
>> > (sic - what's GN?), not that modules themselves are bad.
>> 
>> My suspicion is that it's unusually difficult to implement. It 
>> requires precompiled files to be written out - my experience 
>> with that (precompiled headers) is it is overly complex.
>
> Possibly.  I'm not familiar with C++ modules: what exactly does 
> it entail?  You have to precompile headers before they can be 
> used as a module?  That sounds unusually onerous, compared to, 
> say, D, where the compiler just parses the source file directly 
> and the user doesn't have to do anything extra.
>
>
> T

I'm not too familiar with modules, but the C++ modules really 
have a level of complexity that is staggering to my mind. It's 
not that one file is one module (1:1). That would have been too 
easy ;).

Instead, you can separate modules out over several files (module 
partitions). They form the same module by virtue of having the 
same name in their module statements. But not all partitions are 
equal, either. Some are interfaces (their content is visible 
externally), some internal (their content is only visible 
internally).

Of course, all of this still interacts somehow with header files 
and preprocessor macros.

AFAIK the standard assumes that modules are compiled into some 
kind of self-contained artifacts that can then be imported by 
other modules without a need for separate header files. So in my 
understanding, a compiler has to work with some kind of superset 
of precompiled headers and object files.