X-Git-Url: https://git.distorted.org.uk/~mdw/sgt/putty/blobdiff_plain/6f3bdded24a63651abb39b46e6092c18fb3f5695..5462f4596108c4309fb69b4e57aa1e59d7100908:/doc/udp.but

diff --git a/doc/udp.but b/doc/udp.but
index 8e425616..a543b1dc 100644
--- a/doc/udp.but
+++ b/doc/udp.but
@@ -45,7 +45,10 @@ endianness-dependent operations, and so on.
 \e{don't} care about. In particular, we expect PuTTY to be compiled
 on 32-bit architectures \e{or bigger}; so it's safe to assume that
 \c{int} is at least 32 bits wide, not just the 16 you are guaranteed
-by ANSI C.)
+by ANSI C.  Similarly, we assume that the execution character
+encoding is a superset of the printable characters of ASCII, though
+we don't assume the numeric values of control characters,
+particularly \cw{'\\n'} and \cw{'\\r'}.)
 
 \H{udp-multi-backend} Multiple backends treated equally
 
@@ -75,21 +78,23 @@ Some ports of PuTTY - notably the in-progress Mac port - are
 constrained by the operating system to run as a single process
 potentially managing multiple sessions.
 
-Therefore, the platform-independent parts of PuTTY use \e{hardly
-any} global variables. The very few that do exist, such as
-\c{flags}, are tolerated because they are not specific to a
-particular login session: instead, they define properties that are
-expected to apply equally to \e{all} the sessions run by a single
-PuTTY process. Any data that is specific to a particular network
-session is stored in dynamically allocated data structures, and
-pointers to these structures are passed around between functions.
+Therefore, the platform-independent parts of PuTTY never use global
+variables to store per-session data. The global variables that do
+exist are tolerated because they are not specific to a particular
+login session: \c{flags} defines properties that are expected to
+apply equally to \e{all} the sessions run by a single PuTTY process,
+the random number state in \cw{sshrand.c} and the timer list in
+\cw{timing.c} serve all sessions equally, and so on. But most data
+is specific to a particular network session, and is therefore stored
+in dynamically allocated data structures, and pointers to these
+structures are passed around between functions.
 
 Platform-specific code can reverse this decision if it likes. The
 Windows code, for historical reasons, stores most of its data as
 global variables. That's OK, because \e{on Windows} we know there is
 only one session per PuTTY process, so it's safe to do that. But
 changes to the platform-independent code should avoid introducing
-any more global variables than already exist.
+global variables, unless they are genuinely cross-session.
 
 \H{udp-pure-c} C, not C++