On Tue, 3 Oct 2023, David Malcolm wrote: > As mentioned in my Cauldron talk, this patch adds a call to > diagnostic_show_locus to the "required from here" messages > in print_instantiation_partial_context_line, so that e.g., rather > than the rather mystifying: > > In file included from ../x86_64-pc-linux-gnu/libstdc++-v3/include/memory:78, > from ../../src/demo-1.C:1: > ../x86_64-pc-linux-gnu/libstdc++-v3/include/bits/unique_ptr.h: In instantiation of ‘std::__detail::__unique_ptr_t<_Tp> std::make_unique(_Args&& ...) [with _Tp = bar; _Args = {}; __detail::__unique_ptr_t<_Tp> = __detail::__unique_ptr_t]’: > ../../src/demo-1.C:15:32: required from here > ../x86_64-pc-linux-gnu/libstdc++-v3/include/bits/unique_ptr.h:1066:30: error: no matching function for call to ‘bar::bar()’ > 1066 | { return unique_ptr<_Tp>(new _Tp(std::forward<_Args>(__args)...)); } > | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > ../../src/demo-1.C:10:3: note: candidate: ‘bar::bar(int)’ > 10 | bar (int); > | ^~~ > ../../src/demo-1.C:10:3: note: candidate expects 1 argument, 0 provided > ../../src/demo-1.C:7:7: note: candidate: ‘constexpr bar::bar(const bar&)’ > 7 | class bar : public foo > | ^~~ > ../../src/demo-1.C:7:7: note: candidate expects 1 argument, 0 provided > ../../src/demo-1.C:7:7: note: candidate: ‘constexpr bar::bar(bar&&)’ > ../../src/demo-1.C:7:7: note: candidate expects 1 argument, 0 provided > > we emit: > > In file included from ../x86_64-pc-linux-gnu/libstdc++-v3/include/memory:78, > from ../../src/demo-1.C:1: > ../x86_64-pc-linux-gnu/libstdc++-v3/include/bits/unique_ptr.h: In instantiation of ‘std::__detail::__unique_ptr_t<_Tp> std::make_unique(_Args&& ...) [with _Tp = bar; _Args = {}; __detail::__unique_ptr_t<_Tp> = __detail::__unique_ptr_t]’: > ../../src/demo-1.C:15:32: required from here > 15 | return std::make_unique (); > | ~~~~~~~~~~~~~~~~~~~~~~^~ > ../x86_64-pc-linux-gnu/libstdc++-v3/include/bits/unique_ptr.h:1066:30: error: no matching function for call to ‘bar::bar()’ > 1066 | { return unique_ptr<_Tp>(new _Tp(std::forward<_Args>(__args)...)); } > | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > ../../src/demo-1.C:10:3: note: candidate: ‘bar::bar(int)’ > 10 | bar (int); > | ^~~ > ../../src/demo-1.C:10:3: note: candidate expects 1 argument, 0 provided > ../../src/demo-1.C:7:7: note: candidate: ‘constexpr bar::bar(const bar&)’ > 7 | class bar : public foo > | ^~~ > ../../src/demo-1.C:7:7: note: candidate expects 1 argument, 0 provided > ../../src/demo-1.C:7:7: note: candidate: ‘constexpr bar::bar(bar&&)’ > ../../src/demo-1.C:7:7: note: candidate expects 1 argument, 0 provided > > which shows the code that's leading to the error (the bad call to > std::make_unique). This is great! I noticed however that the source code gets printed in a surprising way in some contexts. Consider: template void f(typename T::type); int main() { f(0); } For this testcase we emit: testcase.C: In function ‘int main()’: testcase.C:4:9: error: no matching function for call to ‘f(int)’ 4 | f(0); | ~~~~~~^~~ testcase.C:1:24: note: candidate: ‘template void f(typename T::type)’ 1 | template void f(typename T::type); | ^ testcase.C:1:24: note: template argument deduction/substitution failed: testcase.C: In substitution of ‘template void f(typename T::type) [with T = int]’: testcase.C:4:9: required from here testcase.C:1:24: note: 4 | f(0); testcase.C:1:24: note: | ~~~~~~^~~ testcase.C:1:24: error: ‘int’ is not a class, struct, or union type 1 | template void f(typename T::type); | ^ In particular the source code part following the "required from here" line testcase.C:4:9: required from here testcase.C:1:24: note: 4 | f(0); testcase.C:1:24: note: | ~~~~~~^~~ seems off, I would have expected it be testcase.C:4:9: required from here 4 | f(0); | ~~~~~~^~~ i.e. without the "testcase.C:1:24: note: " prefix. Does this look expected? (I also wonder if we might want to omit printing the source code altogether in this case, since we already printed that same line earlier during the "no matching function" error?) > > > Successfully bootstrapped & regrtested on x86_64-pc-linux-gnu. > > OK for trunk? > > > gcc/cp/ChangeLog: > * error.cc (print_instantiation_partial_context_line): Call > diagnostic_show_locus. > > gcc/testsuite/ChangeLog: > * g++.dg/diagnostic/static_assert3.C: Add directives for > additional source printing. > * g++.dg/template/error60.C: New test. > > Signed-off-by: David Malcolm > --- > gcc/cp/error.cc | 2 + > .../g++.dg/diagnostic/static_assert3.C | 7 +++- > gcc/testsuite/g++.dg/template/error60.C | 37 +++++++++++++++++++ > 3 files changed, 45 insertions(+), 1 deletion(-) > create mode 100644 gcc/testsuite/g++.dg/template/error60.C > > diff --git a/gcc/cp/error.cc b/gcc/cp/error.cc > index ef96e140f24..767478cf5fd 100644 > --- a/gcc/cp/error.cc > +++ b/gcc/cp/error.cc > @@ -3774,6 +3774,8 @@ print_instantiation_partial_context_line (diagnostic_context *context, > ? _("recursively required from here\n") > : _("required from here\n")); > } > + gcc_rich_location rich_loc (loc); > + diagnostic_show_locus (context, &rich_loc, DK_NOTE); > } > > /* Same as print_instantiation_full_context but less verbose. */ > diff --git a/gcc/testsuite/g++.dg/diagnostic/static_assert3.C b/gcc/testsuite/g++.dg/diagnostic/static_assert3.C > index 5d363884508..4ec53f17120 100644 > --- a/gcc/testsuite/g++.dg/diagnostic/static_assert3.C > +++ b/gcc/testsuite/g++.dg/diagnostic/static_assert3.C > @@ -5,6 +5,11 @@ > template struct is_same { static constexpr bool value = false; }; > template struct is_same { static constexpr bool value = true; }; > > +/* { dg-begin-multiline-output "" } > + f(0, 1.3); > + ~^~~~~~~~ > + { dg-end-multiline-output "" } */ > + > template > void f(T, U) > { > @@ -32,5 +37,5 @@ void f(T, U) > > void g() > { > - f(0, 1.3); > + f(0, 1.3); // { dg-message " required from here" } > } > diff --git a/gcc/testsuite/g++.dg/template/error60.C b/gcc/testsuite/g++.dg/template/error60.C > new file mode 100644 > index 00000000000..8c2139b207c > --- /dev/null > +++ b/gcc/testsuite/g++.dg/template/error60.C > @@ -0,0 +1,37 @@ > +// { dg-options "-fdiagnostics-show-caret" } > + > +template > +struct my_pointer > +{ > + my_pointer (Foo *ptr) // { dg-message " initializing argument 1" } > + : m_ptr (ptr) > + {} > + > + Foo *m_ptr; > +}; > + > +template > +void test (Foo val) > +{ > + my_pointer ptr (val); // { dg-error "invalid conversion from 'int' to 'int\\*'" } > +} > + > +void usage () > +{ > + test (42); // { dg-message " required from here" } > + /* { dg-begin-multiline-output "" } > + test (42); > + ~~~~~~~~~~^~~~ > + { dg-end-multiline-output "" } */ > +} > + > + /* { dg-begin-multiline-output "" } > + my_pointer (Foo *ptr) > + ~~~~~^~~ > + { dg-end-multiline-output "" } */ > + /* { dg-begin-multiline-output "" } > + my_pointer ptr (val); > + ^~~ > + | > + int > + { dg-end-multiline-output "" } */ > -- > 2.26.3 > >