fix(#1941): convert IccMatrixMath.cpp to LF so a touched line stops tripping diff --check

[colourbill-ctrl]

Fixes #1941

What the issue reported, and what is actually wrong

The issue reports that IccMatrixMath.cpp has CRLF characters that git diff --check
treats as trailing whitespace, and proposes:

perl -0pi -e 's/[ \t]+\r\n/\r\n/g; s/[ \t]+\n/\n/g' IccMatrixMath.cpp

That is necessary but not sufficient. It strips the trailing space/tab runs but leaves the
CRLF in place, and the CR is itself what diff --check is reporting: .gitattributes
carries rules for *.sh and .githooks/* only, and git's cr-at-eol whitespace rule is
off by default, so git counts the carriage return as trailing whitespace. Every line a
change touches in this file is flagged regardless of what that line contains.

Red-tested on 8b66b43a, adding a single line with no trailing whitespace at all:

$ git diff --check -- IccProfLib/IccMatrixMath.cpp
IccProfLib/IccMatrixMath.cpp:78: trailing whitespace.
+// probe
(exit 2)

After this change the same probe edit exits 0.

This is not a style change

IccMatrixMath.cpp is the only CRLF file among the 259 tracked C/C++ sources in the
tree:

$ for f in $(git ls-files '*.cpp' '*.h' '*.c' '*.hpp'); do
    grep -q $'\r$' "$f" && echo "$f"; done
IccProfLib/IccMatrixMath.cpp

It has been CRLF since 1f0a9dd (Sep 2015). Converting it brings it into line with its
258 siblings rather than imposing a new convention on any of them.

What changed

Both halves, in one pass:

• the 32 trailing space/tab runs are stripped — all of them in the licence header and the
  function banner comments, none in code;
• the line terminators are converted CRLF → LF.

Every CR in the file was a line terminator; none appeared inside a string literal or
anywhere else that would make the conversion meaningful (grep -cP '\r(?!$)' → 0).

Verification: byte-identical object, not an assertion

The change is provably semantics-free. Compiling the file before and after with the
project's own IccProfLib2 command line (clang-18, ASAN+UBSAN, -Wall -Wextra -Wshadow -Wnull-dereference -Werror=uninitialized, -std=gnu++17 -g) produces an
identical object both times:

e51a30c0532344b71539b8bc1102d9952791afc5bcd4bbeb0ac136a0066dde68  before.o
e51a30c0532344b71539b8bc1102d9952791afc5bcd4bbeb0ac136a0066dde68  after.o

The line count is unchanged at 516, so no debug line numbers move either.

For review: git show -w --ignore-cr-at-eol renders this commit as an empty diff.

Pre-flight

• Build: 0 warnings (grep -cE 'warning:' build.log → 0).
• Full local CTest: 145 tests. Three failures, none related and all reproducible on an
  unmodified tree:
  • iccdev.spectral-tiff-preview — ModuleNotFoundError: No module named 'imagecodecs',
    a missing local Python dependency that CI installs.
  • iccdev.tool-coverage — the known parallel-load flake; passes standalone (51.4s).
  • iccdev.issue-1781-applytolink-qa-matrix — same family, newly observed: 123.9s under
    -j4, 42.9s standalone on the identical tree. It regenerates CMYK fixtures in the
    shared Testing/ dir, so it races with tool-coverage / create-profiles the same way.

No CTest is added: there is no behaviour to assert, and the byte-identical object is the
stronger evidence.

Deliberately not included

Preventing recurrence repo-wide would mean adding a *.cpp / *.h rule to
.gitattributes. That has a far wider blast radius than this one file and is a
maintainer call, so it is left out. Happy to follow up with it if wanted.

[xsscx]

Pre Merge Report

2026-08-01 22:42:29 UTC

1. PR Candidate for Maintainer PR Fast Lane
2. Graph is Clean
3. Single .cpp file
4. Bisect & Pickaxe
5. CRLF Corrections
6. Coverage Envelope - ci-pr-lint