This is the mail archive of the
gcc-patches@gcc.gnu.org
mailing list for the GCC project.
[C++ Patch] fix semi-random template specialization ICE
- From: Alexandre Oliva <aoliva at redhat dot com>
- To: gcc-patches at gcc dot gnu dot org
- Date: Thu, 03 May 2012 15:17:23 -0300
- Subject: [C++ Patch] fix semi-random template specialization ICE
I've recently started getting âlibstdc++-v3/include/functional:2057:63:
internal compiler error: tree check: expected tree_vec, have error_mark
in comp_template_args_with_info, at cp/pt.c:7038â on i686-linux-gnu,
building libstdc++-v3/src/c++11/functexcept.cc -fPIC, at stage1 and on
non-bootstrapped builds. The problem would not occur on
x86_64-linux-gnu with the -m32 multilib.
Jakub reported getting similar errors in the testsuite, but not in the
libstdc++-v3 build.
Bisection revealted the patch that exposed the latent error was r186948,
but I gather it only introduced more potentially-failing specializations
in libstdc++-v3 at spots that wouldn't trigger the bug before.
I couldn't pinpoint the exact source of randomness that causes the build
to fail at precisely the same point on a given machine at a certain
stage, but not on others. What I do know is that it occurs while
iterating on a hash table, which, depending on how the hash is computed,
may explain why we visit some nodes before others depending on
environmentally-deterministic causes.
Anyway, the problem is that, for some unsuitable candidate template
specializations, tsubst returns error_mark_node, which tsubst_decl
stores in argvec, and later on register_specialization gets this
error_mark_node and tries to access it as a tree_vec.
The trivial patch that avoids the misbehavior is returning
error_mark_node as soon as we get that for argvec. Bootstrapped on
i686-pc-linux-gnu and x86_64-linux-gnu, regstrapped on the latter.
Ok to install?
for gcc/cp/ChangeLog
from Alexandre Oliva <aoliva@redhat.com>
* pt.c (tsubst_decl): Bail out if argvec is error_mark_node.
Index: gcc/cp/pt.c
===================================================================
--- gcc/cp/pt.c.orig 2012-04-30 15:34:44.018432544 -0300
+++ gcc/cp/pt.c 2012-04-30 15:34:47.988375071 -0300
@@ -10626,6 +10626,8 @@ tsubst_decl (tree t, tree args, tsubst_f
tmpl = DECL_TI_TEMPLATE (t);
gen_tmpl = most_general_template (tmpl);
argvec = tsubst (DECL_TI_ARGS (t), args, complain, in_decl);
+ if (argvec == error_mark_node)
+ RETURN (error_mark_node);
hash = hash_tmpl_and_args (gen_tmpl, argvec);
spec = retrieve_specialization (gen_tmpl, argvec, hash);
}
--
Alexandre Oliva, freedom fighter http://FSFLA.org/~lxoliva/
You must be the change you wish to see in the world. -- Gandhi
Be Free! -- http://FSFLA.org/ FSF Latin America board member
Free Software Evangelist Red Hat Brazil Compiler Engineer