This is motivated by tooling (clangd, libclang etc) - headers without
declarations are legitimate even if they're not valid TUs.
The other use -x c-header cases (PCH/modules) are nonstandard anyway and this
warning doesn't seem necessary there either.
Differential Revision: https://reviews.llvm.org/D85789
In standard C since C89, a 'translation-unit' is syntactically defined to have
at least one "external-declaration", which is either a decl or a function
definition. In Clang the latter gives us a declaration as well.
The tricky bit about this warning is that our predefines can contain external
declarations (__builtin_va_list and the 128-bit integer types). Therefore our
AST parser now makes sure we have at least one declaration that doesn't come
from the predefines buffer.
Also, remove bogus warning about empty source files. This doesn't catch source
files that only contain comments, and never fired anyway because of our
predefines.
PR12665 and <rdar://problem/9165548>
llvm-svn: 158085
Sam McCall