[24.355]: deactivate enctex when reading \^^ab control sequences.

(Following full description from Petr is slightly edited for English).

Date: Wed, 30 Jul 2014 10:08:40 +0200
From: Petr Olsak
To: Karl Berry

Consider this input file:
-------------------------
\catcode`\{=1 \catcode`\}=2 \catcode`^=7

\mubyte A XY\endmubyte
\mubytein=1 \mubyteout=0 \mubytelog=0
\def\a{\^^58YZ \XYZ XYZ}
\show\a

\end
-------------------------

Then run pdftex -ini -enc ./file.tex

The buggy behavior is:
 \a=macro:
->\AZ \AZ AZ.

because encTeX's conversion XY -> A have to be done *before* tokenisation
as the manual says.  I.e., ^^58 -> X is done *after* encTeX's level
and the good result would be:
 \a=macro:
->\XYZ \AZ AZ.

The consequence of this curious bug is the question at
http://tex.stackexchange.com/questions/191002/csplain-and-url-package-not-working-with-pdftex

Removing this bug isn't trivial because of the bad concept of TeX source
in \S 355 where is "goto start_cs" which returns the reading of the control
sequence to the start and reads again. But the buffer includes the result of
^^ab conversion which is again transformed by encTeX.

I decided to do only a simple correction which supposes that there are
"normal" control sequences and two other types: with encTeX's output in
their names or with ^^ab in their names. Mixing these types is still not
allowed because the implementation needs new data structures and much
code.  IMHO: 1) probability of such mix is almost zero,
2) I don't want to add much code only because of a bad concept
with "goto" in the TeX original code.

The change is "robust" for the case where encTeX isn't in use, because
there is the conditional "if mubyte_in>0" which is false when encTeX
isn't activated.


git-svn-id: svn://tug.org/texlive/trunk@35457 c570f23f-e606-0410-a88d-b1316a301751

2 files changed, 11 insertions, 0 deletions

diff --git a/Build/source/texk/web2c/ChangeLog b/Build/source/texk/web2c/ChangeLog
index 822cb9a225c..cac74597106 100644
--- a/Build/source/texk/web2c/ChangeLog
+++ b/Build/source/texk/web2c/ChangeLog
@@ -1,3 +1,7 @@
+2014-10-28  Karl Berry  <karl@tug.org>
+
+	* enctex.ch: patch for \^^ab control sequences from Petr Olsak.
+
 2014-09-25  Peter Breitenlohner  <peb@mppmu.mpg.de>
 
 	* w2c/config.h: Bug fix: integer64 must always be a 64bit type,
diff --git a/Build/source/texk/web2c/enctex.ch b/Build/source/texk/web2c/enctex.ch
index 13ff30d1faf..c0f5bfe4fa5 100644
--- a/Build/source/texk/web2c/enctex.ch
+++ b/Build/source/texk/web2c/enctex.ch
@@ -315,6 +315,13 @@ begin
 end;
 @z
 
+@x [24.355] - encTeX: deactivated when reading such \^^ab control sequences
+    limit:=limit-d; first:=first-d;
+@y
+    limit:=limit-d; first:=first-d;
+    if mubyte_in>0 then mubyte_keep := k-loc;
+@z
+
 @x [24.356] - encTeX: access the buffer via read_buffer
 begin repeat cur_chr:=buffer[k]; cat:=cat_code(cur_chr); incr(k);
 until (cat<>letter)or(k>limit);