https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90410
Bug ID: 90410
Summary: [feature request] -fdiagnostics-show-template-tree
should expand mismatched reference parameters
Product: gcc
Version: 8.2.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: m101010a at gmail dot com
Target Milestone: ---
$ cat x.cpp
template<class,class> struct s{};
void byval(s<long,long>);
void byref(s<long,long>&);
void bycref(const s<long,long>&);
void g(s<int,long> v)
{
byval(v);
byref(v);
bycref(v);
}
$ g++ -fsyntax-only -fdiagnostics-show-template-tree x.cpp
x.cpp: In function 'void g(s<int, long int>)':
x.cpp:7:11: error: could not convert 'v' from 's<int,[...]>' to 's<long
int,[...]>'
s<
[int != long int],
[...]>
byval(v);
^
x.cpp:8:11: error: invalid initialization of reference of type 's<long int,
long int>&' from expression of type 's<int, long int>'
byref(v);
^
x.cpp:3:6: note: in passing argument 1 of 'void byref(s<long int, long int>&)'
void byref(s<long,long>&);
^~~~~
x.cpp:9:12: error: invalid initialization of reference of type 'const s<long
int, long int>&' from expression of type 's<int, long int>'
bycref(v);
^
x.cpp:4:6: note: in passing argument 1 of 'void bycref(const s<long int, long
int>&)'
void bycref(const s<long,long>&);
^~~~~~
$ g++ -v
Using built-in specs.
COLLECT_GCC=g++
COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-pc-linux-gnu/8.2.1/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: /build/gcc/src/gcc/configure --prefix=/usr --libdir=/usr/lib
--libexecdir=/usr/lib --mandir=/usr/share/man --infodir=/usr/share/info
--with-bugurl=https://bugs.archlinux.org/
--enable-languages=c,c++,ada,fortran,go,lto,objc,obj-c++ --enable-shared
--enable-threads=posix --enable-libmpx --with-system-zlib --with-isl
--enable-__cxa_atexit --disable-libunwind-exceptions --enable-clocale=gnu
--disable-libstdcxx-pch --disable-libssp --enable-gnu-unique-object
--enable-linker-build-id --enable-lto --enable-plugin
--enable-install-libiberty --with-linker-hash-style=gnu
--enable-gnu-indirect-function --enable-multilib --disable-werror
--enable-checking=release --enable-default-pie --enable-default-ssp
--enable-cet=auto
Thread model: posix
gcc version 8.2.1 20181127 (GCC)
When taking s by value, -fdiagnostics-show-template-tree expands the template
tree and shows exactly which parts differ between the declaration and the
caller. When taking s by reference the tree is not expanded, and the similar
parts are not elided.
This behavior started in GCC 8.1 and persists in 9.1 and trunk.
