From: Alexei Sheplyakov <Alexei.Sheplyakov@gmail.com>
Date: Tue, 1 Jul 2014 18:46:11 +0000 (+0300)
Subject: [bugfix] log_series: avoid infinite recursion
X-Git-Tag: release_1-6-3~11
X-Git-Url: https://www.ginac.de/ginac.git//ginac.git?p=ginac.git;a=commitdiff_plain;h=13964f3416ec9de8829b57d4a2bbd9fe9a6db4ef;hp=edfa67d26bac695b5ef9911f3cda3ff50232e35a;ds=sidebyside

[bugfix] log_series: avoid infinite recursion

Check if the argument is on a branch cut check if it actually depends
on the expansion variable before trying to expand around a different
point in order to avoid the infinite recursion (or rather a segfault
due to a stack overflow).

Thanks to Mario Prausa for a bugreport.
---

diff --git a/check/exam_inifcns.cpp b/check/exam_inifcns.cpp
index 3a1a36b5..2fe28415 100644
--- a/check/exam_inifcns.cpp
+++ b/check/exam_inifcns.cpp
@@ -318,6 +318,15 @@ static unsigned inifcns_consist_log()
 	if (ex(log(pow(a,b))).is_equal(b*log(a)))
 		++result;
 
+	// infinite recursion log_series
+	ex e(log(-p));
+	ex ser = ex_to<pseries>(e.series(z, 1))
+		.convert_to_poly(/* no_order = */ true);
+	if (!ser.is_equal(e)) {
+		clog << "series(" << e << ", " << z << "): wrong result" << endl;
+		++result;
+	}
+
 	return result;
 }
 
diff --git a/ginac/inifcns_trans.cpp b/ginac/inifcns_trans.cpp
index c5551f75..682a981b 100644
--- a/ginac/inifcns_trans.cpp
+++ b/ginac/inifcns_trans.cpp
@@ -204,6 +204,10 @@ static ex log_series(const ex &arg,
 	if (arg_pt.is_zero())
 		must_expand_arg = true;
 	
+	if (arg.diff(ex_to<symbol>(rel.lhs())).is_zero()) {
+		throw do_taylor();
+	}
+
 	if (must_expand_arg) {
 		// method:
 		// This is the branch point: Series expand the argument first, then