From aa1b8d31acbcc7630e1ca2f2bbd27eeb34b00446 Mon Sep 17 00:00:00 2001 From: Mark Levedahl Date: Fri, 14 Mar 2025 11:45:35 -0400 Subject: [PATCH] gitk: use -profile tcl8 for file input with Tcl 9 gitk invokes many git commands expecting output in utf-8 encoding, but git accepts extended ascii (code page unknown) as utf-8 without validating, so cannot guarantee valid utf-8 on output. In particular, using any extended ascii code page, of which there are many, has long been acceptable given that everyone on a project is aware of and uses that same code page to view all data. utf-8 accepts only 7-bit ascii characters in single bytes, and any characters outside of that base set require at least two bytes. Tcl is a string based language, and transcodes all input data to an internal unicode format, and to whatever format is requested on output: "pure" binary is recoded using iso8859-1. Tcl8.x silently recodes invalid utf-8 as binary data, so extended ascii characters maintain their binary value on output but may not display correctly. Tcl 8.7 added three profiles to control this behaviour: strict (raises exceptions), replace (replaces each invalid byte with ?), and the default tcl8 maintaining the old behavior. Tcl 9 changes the default profile to strict, meaning any invalid utf-8 raises an exception that gitk does not handle. An example of this in the git repository is commit 7eb93c8965 ("[PATCH] Simplify git script", 2005-09-07). This includes extended ascii characters in the author name and commit message. As a result, gitk + Tcl 9 cannot view the git repository at any point beyond that commit. Note: Tcl 9.0 has a bug, to be fixed in 9.1, where this particular condition results in a memory error causing Tcl to crash [1]. The tcl8 profile used so far has acceptable behavior given gitk's acceptance: this allows gitk to accept extended ascii though it may display incorrectly. Let's continue that behavior by overriding open to use the tcl8 profile on Tcl9 and later: Tcl 8.6 does not understand fconfigure -profile, and Tcl 8.7 maintains the tcl8 profile. [1] Per https://core.tcl-lang.org/tcl/tktview/73bb42fb3f35cd613af6fcea465e35bbfd352216 Signed-off-by: Mark Levedahl --- gitk | 13 +++++++++++++ 1 file changed, 13 insertions(+) diff --git a/gitk b/gitk index d9812f2e9c..342b0aba8d 100755 --- a/gitk +++ b/gitk @@ -33,6 +33,19 @@ The version of git found is $git_version." exit 1 } +###################################################################### +## Enable Tcl8 profile in Tcl9, allowing consumption of data that has +## bytes not conforming to the assumed encoding profile. + +if {[package vcompare $::tcl_version 9.0] >= 0} { + rename open _strict_open + proc open args { + set f [_strict_open {*}$args] + chan configure $f -profile tcl8 + return $f + } +} + ###################################################################### ## ## Enabling platform-specific code paths -- 2.47.3