From: Alexei Sheplyakov <alexei.sheplyakov@gmail.com>
Date: Mon, 4 Oct 2010 07:21:05 +0000 (+0200)
Subject: Avoid infinite loop when unarchiving realsymbol and possymbol.
X-Git-Tag: release_1-6-0~18^2~1^2~6
X-Git-Url: https://www.ginac.de/ginac.git//ginac.git?p=ginac.git;a=commitdiff_plain;h=c40c54f17b68f79ee42833adb3364970385e2caa

Avoid infinite loop when unarchiving realsymbol and possymbol.

symbol::read_archive(): explicitly set status_flags::evaluated (and
status_flags::expanded) on object being unarchived. These flags get
reset by basic::operator=(const basic&) for realsymbol and possymbol,
and nothing sets (except symbol ctor), so automatic evaluation never
terminates (or rather, terminates due to a stack overflow). Therefore
it's necessary need to set status_flags::evaluated explicitly.

Thanks to Markus Fröb for a bugreport and a test case.
(cherry picked from commit e99d0d58c1bbaa8ee73e4a90a90aa1086f2f813d)
---

diff --git a/ginac/symbol.cpp b/ginac/symbol.cpp
index 9897bb4c..c9db110f 100644
--- a/ginac/symbol.cpp
+++ b/ginac/symbol.cpp
@@ -109,6 +109,15 @@ void symbol::read_archive(const archive_node &n, lst &sym_lst)
 	for (lst::const_iterator it = sym_lst.begin(); it != sym_lst.end(); ++it) {
 		if (is_a<symbol>(*it) && (ex_to<symbol>(*it).name == tmp_name)) {
 			*this = ex_to<symbol>(*it);
+			// XXX: This method is responsible for reading realsymbol
+			// and possymbol objects too. But
+			// basic::operator=(const basic& other)
+			// resets status_flags::evaluated if other and *this are
+			// of different types. Usually this is a good idea, but
+			// doing this for symbols is wrong (for one, nothing is
+			// going to set status_flags::evaluated, evaluation will
+			// loop forever). Therefore we need to restore flags.
+			setflag(status_flags::evaluated | status_flags::expanded);
 			return;
 		}
 	}