ASBI Pocket Beit Midrash: Aruch HaShulhan, Laws of Synagogue 151:2

(2) We do not eat and we do not drink in them, even a temporary (short) consumption. We do not get dressed in them and we do not travel through them. We do not use them to take shelter from the heat when it is hot outside or from the rain when it is raining. Learned ones and their students are allowed to eat in them in urgent situations. Some say that they can eat in a study hall, even if the situation is not urgent, since for most of the day, they will be there to learn anyway. If so [if they would have to leave], this would be a waste of [ time that could be spent learning] Torah when they would have to step out of there to eat. However, to take shelter there from the rain or from the heat or cold is still prohibited, even for a learned person. Rather, he would have to learn there, or in a Synagogue, he would have to pray there (Magen Avraham subsection 2). There is in the Yerushalmi that a learned person is allowed lodge in a study hall (Magen Avraham subsection 2). And like this it sounds like in Pesachim (Pesachim 100a). At seems that guests can eat in the study hall. However, in truth, the Tosfos write there that this is referring to the rooms next to the Synagogue, see there. (Refer to the Ta"z subsection 1. His words are puzzling. In addition, the Ramban did not write this, just because of a condition, see there.)