[libcxx-commits] [PATCH] D119329: [libc++] Prepare string.modifiers tests for constexpr

[Louis Dionne via Phabricator via libcxx-commits]

ldionne added inline comments.


================
Comment at: libcxx/test/std/strings/basic.string/string.modifiers/string_insert/size_T_size_size.pass.cpp:1833
+template <class S, class SV>
+void test() {
+  test0<S, SV>();
----------------
philnik wrote:
> Quuxplusone wrote:
> > philnik wrote:
> > > ldionne wrote:
> > > > Instead, can you do
> > > > 
> > > > ```
> > > > template <class S, class V>
> > > > _LIBCPP_CONSTEXPR_AFTER_CXX17 void tests() {
> > > >   test0<S, SV>();
> > > >   // ...
> > > >   test31<S, SV>();
> > > > }
> > > > 
> > > > bool check_all() {
> > > >   tests<std::string, std::string_view>();
> > > > #if TEST_STD_VER >= 11
> > > >   tests<std::basic_string<char, std::char_traits<char>, min_allocator<char>>,
> > > >         std::basic_string_view<char, std::char_traits<char>>>();
> > > > #endif
> > > >   return true;
> > > > }
> > > > 
> > > > int main() {
> > > >   check_all();
> > > > #if TEST_STD_VER > 17
> > > >   static_assert(check_all());
> > > > #endif
> > > > }
> > > > ```
> > > > 
> > > > You can also tweak `test31` to be templated like the other ones, I think you only need to use the `SV()` macro and friends in it.
> > > I can't, because you can "only" do about 1 million steps during constant evaluation. If everything is in a single `static_assert()` that limit is reached. I can of course make test 31 a template.
> > FWIW, a quick skim did not enlighten me as to why we need exactly these 32 opaquely numbered test cases here. What's the purpose of each of these tests? Can we get the "length" of this test down below a million simply by improving it?
> > I see we might want to test every possible cell in the matrix (short,long) x (0,1,3,n-1,n,n+1) x (short,long) x (0,1,3,n-1,n,n+1) x (0,1,2,3,4,n-1,n,n+1) but even that's only 1152 different test cases, and we've got 1843 //lines// in the left-hand file here.
> I don't think we would get it below a million without decreasing test coverage. If I remember correctly clang compiled about the first 10 functions until it errored. Anyways, that's definitely out of scope for this PR.
> I can't, because you can "only" do about 1 million steps during constant evaluation. If everything is in a single `static_assert()` that limit is reached. I can of course make test 31 a template.

Interesting -- things are never as simple as they seem.

I'd still like for `test31` to be a template, like the other ones.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D119329/new/

https://reviews.llvm.org/D119329