[GiNaC-devel] [PATCH] [bugfix] Avoid infinite loop when unarchiving realsymbol and possymbol.

[Alexei Sheplyakov]

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.

---
 ginac/symbol.cpp |    9 +++++++++
 1 files changed, 9 insertions(+), 0 deletions(-)

diff --git a/ginac/symbol.cpp b/ginac/symbol.cpp
index 9897bb4..8d05238 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;
 		}
 	}
-- 
1.7.1