I've recently started getting “libstdc++-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:7038” 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 <aol...@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
