1 files changed, 91 insertions, 4 deletions
diff --git a/macros/latex-dev/base/ltboxes.dtx b/macros/latex-dev/base/ltboxes.dtx
index ff1717caa9..d84158c161 100644
--- a/macros/latex-dev/base/ltboxes.dtx
+++ b/macros/latex-dev/base/ltboxes.dtx
@@ -33,7 +33,7 @@
 %<*driver>
 % \fi
 \ProvidesFile{ltboxes.dtx}
-             [2022/09/07 v1.4d LaTeX Kernel (Box Commands)]
+             [2023/10/26 v1.4e LaTeX Kernel (Box Commands)]
 % \iffalse
 \documentclass{ltxdoc}
 \GetFileInfo{ltboxes.dtx}
@@ -342,13 +342,36 @@
 % \begin{macro}{\@imakebox}
 % \changes{v0.1a}{1993/12/03}
 %         {macro modified}
+% \changes{v1.4e}{2023/10/26}
+%         {Guard against unknown alignment gh/1072}
 % Internal form of |\makebox|.
 %    \begin{macrocode}
+%</2ekernel>
+%<latexrelease>\IncludeInRelease{2023/11/01}%
+%<latexrelease>                 {\@imakebox}{Unknown alignment warning}%
+%<*2ekernel|latexrelease>
 \long\def\@imakebox[#1][#2]#3{%
   \@begin@tempboxa\hbox{#3}%
     \setlength\@tempdima{#1}%       support calc
-    \hb@xt@\@tempdima{\csname bm@#2\endcsname}%
+    \hb@xt@\@tempdima{%
+     \expandafter\ifx\csname bm@#2\endcsname\relax
+       \bm@c
+       \@latex@warning{Unexpected alignment #2}%
+     \else
+       \csname bm@#2\endcsname
+     \fi}%
   \@end@tempboxa}
+%</2ekernel|latexrelease>
+%<latexrelease>\EndIncludeInRelease
+%<latexrelease>\IncludeInRelease{0000/00/00}%
+%<latexrelease>                 {\@imakebox}{Unknown alignment warning}%
+%<latexrelease>\long\def\@imakebox[#1][#2]#3{%
+%<latexrelease>  \@begin@tempboxa\hbox{#3}%
+%<latexrelease>    \setlength\@tempdima{#1}%       support calc
+%<latexrelease>    \hb@xt@\@tempdima{\csname bm@#2\endcsname}%
+%<latexrelease>  \@end@tempboxa}
+%<latexrelease>\EndIncludeInRelease
+%<*2ekernel>
 %    \end{macrocode}
 % \end{macro}
 %
@@ -748,19 +771,46 @@
 %         {\cs{leavevmode} moved to \cs{@frameb@x}}
 % \changes{v1.0s}{1995/04/27}
 %         {Move \cs{leavevmode} for graphics/1512}
+% \changes{v1.4e}{2023/10/26}
+%         {Guard against unknown alignment gh/1072}
 %    In order to set the whole box, including the frame to the
 %    specified dimension, we first determine that dimension
 %    from the natural size of the text, |#3|.
 %    calculated width.
 %    \begin{macrocode}
+%</2ekernel>
+%<latexrelease>\IncludeInRelease{2023/11/01}%
+%<latexrelease>                 {\@iframebox}{Unknown alignment warning}%
+%<*2ekernel|latexrelease>
 \long\def\@iframebox[#1][#2]#3{%
   \leavevmode
   \@begin@tempboxa\hbox{#3}%
     \setlength\@tempdima{#1}%
     \setbox\@tempboxa\hb@xt@\@tempdima
-         {\kern\fboxsep\csname bm@#2\endcsname\kern\fboxsep}%
+         {\kern\fboxsep
+          \expandafter\ifx\csname bm@#2\endcsname\relax
+            \bm@c
+            \@latex@warning{Unexpected alignment #2}%
+          \else
+            \csname bm@#2\endcsname
+          \fi
+          \kern\fboxsep}%
     \@frameb@x{\kern-\fboxrule}%
   \@end@tempboxa}
+%</2ekernel|latexrelease>
+%<latexrelease>\EndIncludeInRelease
+%<latexrelease>\IncludeInRelease{0000/00/00}%
+%<latexrelease>                 {\@iframebox}{Unknown alignment warning}%
+%<latexrelease>\long\def\@iframebox[#1][#2]#3{%
+%<latexrelease>  \leavevmode
+%<latexrelease>  \@begin@tempboxa\hbox{#3}%
+%<latexrelease>    \setlength\@tempdima{#1}%
+%<latexrelease>    \setbox\@tempboxa\hb@xt@\@tempdima
+%<latexrelease>         {\kern\fboxsep\csname bm@#2\endcsname\kern\fboxsep}%
+%<latexrelease>    \@frameb@x{\kern-\fboxrule}%
+%<latexrelease>  \@end@tempboxa}
+%<latexrelease>\EndIncludeInRelease
+%<*2ekernel>
 %    \end{macrocode}
 % \end{macro}
 %
@@ -881,9 +931,17 @@
 % \changes{v1.1g}{2006/05/18}
 %         {Ensure \cs{@parboxto} holds the value of \cs{@tempdimb} not the
 %          register itself (pr/3867)}
+% \changes{v1.4e}{2023/10/26}
+%         {Guard against unknown alignment gh/1072}
 % The internal version of |\parbox|.
 %    \begin{macrocode}
 \let\@parboxto\@empty
+%    \end{macrocode}
+%    \begin{macrocode}
+%</2ekernel>
+%<latexrelease>\IncludeInRelease{2023/11/01}%
+%<latexrelease>                 {\@iiiparbox}{Unknown alignment warning}%
+%<*2ekernel|latexrelease>
 \long\def\@iiiparbox#1#2[#3]#4#5{%
   \leavevmode
   \@pboxswfalse
@@ -899,9 +957,38 @@
     \else\@pboxswtrue $\vcenter
     \fi\fi\fi
     \@parboxto{\let\hss\vss\let\unhbox\unvbox
-       \csname bm@#3\endcsname}%
+     \expandafter\ifx\csname bm@#3\endcsname\relax
+       \bm@c
+       \@latex@warning{Unexpected alignment #3}%
+     \else
+       \csname bm@#3\endcsname
+     \fi}%
     \if@pboxsw \m@th$\fi
   \@end@tempboxa}
+%</2ekernel|latexrelease>
+%<latexrelease>\EndIncludeInRelease
+%<latexrelease>\IncludeInRelease{0000/00/00}%
+%<latexrelease>                 {\@iiiparbox}{Unknown alignment warning}%
+%<latexrelease>\long\def\@iiiparbox#1#2[#3]#4#5{%
+%<latexrelease>  \leavevmode
+%<latexrelease>  \@pboxswfalse
+%<latexrelease>  \setlength\@tempdima{#4}%
+%<latexrelease>  \@begin@tempboxa\vbox{\hsize\@tempdima\@parboxrestore#5\@@par}%
+%<latexrelease>    \ifx\relax#2\else
+%<latexrelease>      \setlength\@tempdimb{#2}%
+%<latexrelease>      \edef\@parboxto{to\the\@tempdimb}%
+%<latexrelease>    \fi
+%<latexrelease>    \if#1b\vbox
+%<latexrelease>    \else\if #1t\vtop
+%<latexrelease>    \else\ifmmode\vcenter
+%<latexrelease>    \else\@pboxswtrue $\vcenter
+%<latexrelease>    \fi\fi\fi
+%<latexrelease>    \@parboxto{\let\hss\vss\let\unhbox\unvbox
+%<latexrelease>       \csname bm@#3\endcsname}%
+%<latexrelease>    \if@pboxsw \m@th$\fi
+%<latexrelease>  \@end@tempboxa}
+%<latexrelease>\EndIncludeInRelease
+%<*2ekernel>
 %    \end{macrocode}
 % \end{macro}
 % \end{macro}