| Summary: | Endless operator-> chain causes infinite loop | ||
|---|---|---|---|
| Product: | gcc | Reporter: | David Krauss <potswa> |
| Component: | c++ | Assignee: | Not yet assigned to anyone <unassigned> |
| Status: | RESOLVED FIXED | ||
| Severity: | normal | CC: | basil, jason |
| Priority: | P3 | ||
| Version: | 4.5.1 | ||
| Target Milestone: | 4.7.0 | ||
| See Also: | https://gcc.gnu.org/bugzilla/show_bug.cgi?id=55581 | ||
| Host: | Target: | ||
| Build: | Known to work: | ||
| Known to fail: | Last reconfirmed: | 2011-05-23 10:58:00 | |
| Attachments: |
Patch fixes behavior but error message repeats twice.
replace crufty previous patch |
||
For the record, ICC (EDG that is) misbehaves the same way, at least the versions to which I have access. Maybe clang does something different? nope, same behaviour for clang 2.8 Confirmed at least. Created attachment 24359 [details]
Patch fixes behavior but error message repeats twice.
I implemented the suggested fix, but the resulting error message repeats the part about "template instantiation depth exceeds maximum" twice. The template backtrace appears after the error, not before as with a usual nesting problem. Is there something I'm obviously doing wrong here?
Here are the most relevant lines from the attached patch.
/* For diagnostic purposes, pretend that the chain is nested. */
if (CLASS_TYPE_P (chain_type) && CLASSTYPE_TEMPLATE_INFO (chain_type))
push_tinst_level (chain_type);
Created attachment 24360 [details]
replace crufty previous patch
See this patch instead. Previous unintentionally captured unrelated development.
Maybe Jason can give you some tips, better sending the patch to the mailing list for that, though, Bugzilla isn't meant for patches. CC Jason. Yes, I'll likely do that in a few days… just wanted to put the code in "safe holding," just in case. Author: jason Date: Fri Jun 10 05:18:36 2011 New Revision: 174889 URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=174889 Log: PR c++/49118 * typeck2.c (build_x_arrow): Push fake template context to produce diagnostic on acyclic endless operator-> drill-down. * call.c (build_new_op): Change Boolean overload status value to a pointer to the overload function. * cp-tree.h: Likewise. * typeck.c: Likewise. * parser.c: Likewise. * decl2.c: Likewise. * pt.c: Likewise. Added: trunk/gcc/testsuite/g++.dg/template/arrow1.C Modified: trunk/gcc/cp/ChangeLog trunk/gcc/cp/call.c trunk/gcc/cp/cp-tree.h trunk/gcc/cp/decl2.c trunk/gcc/cp/parser.c trunk/gcc/cp/pt.c trunk/gcc/cp/typeck.c trunk/gcc/cp/typeck2.c trunk/gcc/testsuite/ChangeLog Thanks!
On Jun 9, 2011, at 10:18 PM, jason at gcc dot gnu.org wrote:
> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49118
Fixed for 4.7. *** Bug 56449 has been marked as a duplicate of this bug. *** |
When the "drill-down" behavior is used to chain operator-> calls, a cycle in the chain causes an immediate error message, but an endless acyclic chain causes the compiler to hang, very slowly consuming memory. Minimal case: template< int n > struct a { a< n+1 > operator->() { return a< n+1 >(); } }; int main() { a<0>()->x; } Suggested fix: If operator-> returns a template specialization, consider its instantiation to be nested. This existing error message and limit-mechanism would be appropriate: error: template instantiation depth exceeds maximum of 500 (use -ftemplate-depth-NN to increase the maximum) instantiating ‘struct a<500>’