88cfd531c6
My r10-7007 patch tweaked tsubst not to reduce the template level of
template parameters when tf_partial. That caused infinite looping in
is_specialization_of: we ended up with a class template specialization
whose TREE_TYPE (CLASSTYPE_TI_TEMPLATE (t)) == t, so the second for
loop in is_specialization_of never finished.
There's a lot going on in this test, but essentially: the template fn
here has two template parameters, we call it with one explicitly
provided, the other one has to be deduced. So we'll find ourselves
in fn_type_unification which uses tf_partial when tsubsting the
*explicit* template arguments into the function type. That leads to
tsubstituting the return type, C<T>. C is a member template; its
most general template is
template<class U> template<class V> struct B<U>::C
we figure out (tsubst_template_args) that the template argument list
is <int, int>. They come from different levels, one comes from B<int>,
the other one from fn<int>.
So now we lookup_template_class to see if we have C<int, int>. We
do the
/* This is a full instantiation of a member template. Find
the partial instantiation of which this is an instance. */
TREE_VEC_LENGTH (arglist)--;
// arglist is now <int>, not <int, int>
found = tsubst (gen_tmpl, arglist, complain, NULL_TREE);
TREE_VEC_LENGTH (arglist)++;
magic which is looking for the partial instantiation, in this case,
that would be template<class V> struct B<int>::C. Note we're still
in a tf_partial context! So the tsubst_template_args in the tsubst
(which tries to substitute <int> into <U, V>) returns <int, V>, but
V's template level hasn't been reduced! After tsubst_template_args,
tsubst_template_decl looks to see if we already have this specialization:
// t = template_decl C
// full_args = <int, V>
spec = retrieve_specialization (t, full_args, hash);
but doesn't find the one we created a while ago, when processing
B<int> b; in the test, because V's levels don't match. Whereupon
tsubst_template_decl creates a new TEMPLATE_DECL, one that leads to
the infinite looping problem.
Fixed by using tf_none when looking for an existing partial instantiation.
It also occurred to me that I should be able to trigger a similar
problem with 'auto', since r10-7007 removed an is_auto check. And lo,
I constructed deduce10.C which exhibits the same issue with pre-r10-7007
compilers. This patch fixes that problem as well. I'm ecstatic.
gcc/cp/ChangeLog:
PR c++/95888
* pt.c (lookup_template_class_1): Pass tf_none to tsubst when looking
for the partial instantiation.
gcc/testsuite/ChangeLog:
PR c++/95888
* g++.dg/template/deduce10.C: New test.
* g++.dg/template/deduce9.C: New test.
|
||
|---|---|---|
| c++tools | ||
| config | ||
| contrib | ||
| fixincludes | ||
| gcc | ||
| gnattools | ||
| gotools | ||
| include | ||
| INSTALL | ||
| intl | ||
| libada | ||
| libatomic | ||
| libbacktrace | ||
| libcc1 | ||
| libcody | ||
| libcpp | ||
| libdecnumber | ||
| libffi | ||
| libgcc | ||
| libgfortran | ||
| libgo | ||
| libgomp | ||
| libhsail-rt | ||
| libiberty | ||
| libitm | ||
| libobjc | ||
| liboffloadmic | ||
| libphobos | ||
| libquadmath | ||
| libsanitizer | ||
| libssp | ||
| libstdc++-v3 | ||
| libvtv | ||
| lto-plugin | ||
| maintainer-scripts | ||
| zlib | ||
| .dir-locals.el | ||
| .gitattributes | ||
| .gitignore | ||
| ABOUT-NLS | ||
| ar-lib | ||
| ChangeLog | ||
| ChangeLog.jit | ||
| ChangeLog.tree-ssa | ||
| compile | ||
| config-ml.in | ||
| config.guess | ||
| config.rpath | ||
| config.sub | ||
| configure | ||
| configure.ac | ||
| COPYING | ||
| COPYING3 | ||
| COPYING3.LIB | ||
| COPYING.LIB | ||
| COPYING.RUNTIME | ||
| depcomp | ||
| install-sh | ||
| libtool-ldflags | ||
| libtool.m4 | ||
| lt~obsolete.m4 | ||
| ltgcc.m4 | ||
| ltmain.sh | ||
| ltoptions.m4 | ||
| ltsugar.m4 | ||
| ltversion.m4 | ||
| MAINTAINERS | ||
| Makefile.def | ||
| Makefile.in | ||
| Makefile.tpl | ||
| missing | ||
| mkdep | ||
| mkinstalldirs | ||
| move-if-change | ||
| multilib.am | ||
| README | ||
| symlink-tree | ||
| test-driver | ||
| ylwrap | ||
This directory contains the GNU Compiler Collection (GCC). The GNU Compiler Collection is free software. See the files whose names start with COPYING for copying permission. The manuals, and some of the runtime libraries, are under different terms; see the individual source files for details. The directory INSTALL contains copies of the installation information as HTML and plain text. The source of this information is gcc/doc/install.texi. The installation information includes details of what is included in the GCC sources and what files GCC installs. See the file gcc/doc/gcc.texi (together with other files that it includes) for usage and porting information. An online readable version of the manual is in the files gcc/doc/gcc.info*. See http://gcc.gnu.org/bugs/ for how to report bugs usefully. Copyright years on GCC source files may be listed using range notation, e.g., 1987-2012, indicating that every year in the range, inclusive, is a copyrightable year that could otherwise be listed individually.