Commits on Apr 26, 2022

1. Header file cleanup for C++20 header-units …

   C++20 adds 'header units' as a stepping-stone to modules.  Header
   units are regular header-files that have a 'self-contained' property
   -- they do not require previously-included headers to provide typedefs
   and what not.
   
   This addresses 2 problems discovered when using clang modules (as a
   proxy for C++20 header-units).
   
   a) Some headers that pay attention to OPENSSL_NO_STDIO to determine
   whether to declare certain FILE*-taking functions do not #include
   <stdio.h> themselves, relying on their includer already having done
   that.  That breaks the above mentioned encapuslation requirement.
   Fixed by conditionally including stdio.h in those headers.  I chose to
   always include stdio.h in such headers, even when they included
   another such header that transitively included stdio.  That way they
   do not rely on an artifact of that intermediate header's behaviour.
   
   b) Some headers have #includes inside 'extern "C" { ... }' regions.
   That has a bad code-smell, but GCC and clang have extensions to permit
   it with implementation-defined effects.  Clang needs annotation on the
   included files to know that they themselves are entirely inside a
   similar region.  GCC behavesq as-if there's an extern "C++" region
   wrapping the included header (which must therefore wrap its contents
   in extern "C", if that is what it wants.  In effect the includer's
   extern "C" region is just misleading. I didn't audit all the headers
   for this, only those I noticed when addressing #a.
   
   \#a is necessary to build the headers as a set of clang-modules.  #b
   is not necessary, but as I mentioned, avoids potentially
   implementation-defined behaviour.

   

   urnathan committed Apr 26, 2022
   Copy the full SHA

   f81a634 View commit details

   Browse the repository at this point in the history