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From 8c014bceeca6a558519e86b16a8142accc41e94f Mon Sep 17 00:00:00 2001
From: jason <jason@138bc75d-0d04-0410-961f-82ee72b054a4>
Date: Thu, 28 Jun 2018 00:25:21 +0000
Subject: [PATCH] PR c++/80290 - memory-hog with std::pair.
* pt.c (type_unification_real): Skip non-dependent conversion
check for a nested list argument.
(braced_init_depth): New.
Upstream-Status: Backport
Signed-off-by: Joel Stanley <joel@jms.id.au>
---
gcc/cp/pt.c | 22 ++++++++++++++++++++++
1 file changed, 22 insertions(+)
diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index 79cfd0129226..71077a3b0498 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -19242,6 +19242,24 @@ try_array_deduction (tree tparms, tree targs, tree parm)
/*nondeduced*/false, array_deduction_r);
}
+/* Returns how many levels of { } INIT contains. */
+
+static int
+braced_init_depth (tree init)
+{
+ if (!init || !BRACE_ENCLOSED_INITIALIZER_P (init))
+ return 0;
+ unsigned i; tree val;
+ unsigned max = 0;
+ FOR_EACH_CONSTRUCTOR_VALUE (CONSTRUCTOR_ELTS (init), i, val)
+ {
+ unsigned elt_d = braced_init_depth (val);
+ if (elt_d > max)
+ max = elt_d;
+ }
+ return max + 1;
+}
+
/* Most parms like fn_type_unification.
If SUBR is 1, we're being called recursively (to unify the
@@ -19478,6 +19496,10 @@ type_unification_real (tree tparms,
if (uses_template_parms (parm))
continue;
+ /* Workaround for c++/80290: avoid combinatorial explosion on
+ deeply nested braced init-lists. */
+ if (braced_init_depth (arg) > 2)
+ continue;
if (check_non_deducible_conversion (parm, arg, strict, flags,
explain_p))
return 1;
--
2.17.1
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