Commit: CI: Add C preproc indentation check to CI

[Christian Brabandt]

CI: Add C preproc indentation check to CI

Commit: https://github.com/vim/vim/commit/1d4fe89054ac15ce19c2ed884bf013640a836bb5
Author: Hirohito Higashi <h.eas...@gmail.com>
Date: Tue Jan 13 21:22:27 2026 +0000

CI: Add C preproc indentation check to CI

closes: https://github.com/vim/vim/issues/19165

Signed-off-by: Hirohito Higashi <h.eas...@gmail.com>
Signed-off-by: Christian Brabandt <c...@256bit.org>

diff --git a/.github/MAINTAINERS b/.github/MAINTAINERS
index 048445721..733c9af1c 100644
--- a/.github/MAINTAINERS
+++ b/.github/MAINTAINERS
@@ -699,6 +699,7 @@ runtime/syntax/xs.vim @petdance
runtime/syntax/xslt.vim @Boobies
runtime/syntax/zserio.vim @dpelle
runtime/syntax/zsh.vim @chrisbra
+runtime/tools/preproc_indent.vim @h-east
runtime/tutor/tutor1.eo @dpelle
runtime/tutor/tutor1.fr @dpelle
runtime/tutor/tutor1.ru @RestorerZ
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index b1faa0273..6759ec9a0 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -84,7 +84,7 @@ jobs:
architecture: arm64
- features: normal
compiler: gcc
- extra: [vimtags, proto]
+ extra: [vimtags, proto, preproc_indent]
- features: huge
compiler: gcc
extra: [no_x11_wl]
@@ -363,6 +363,16 @@ jobs:
true
)

+ - name: Check preprocessor indent
+ if: contains(matrix.extra, 'preproc_indent')
+ run: |
+ # This will exit with an error code if the files differ from source
+ (
+ "${SRCDIR}"/vim -u NONE --not-a-term -esNX +"cd runtime/tools" -S preproc_indent.vim
+ git diff --exit-code -- src/*.[ch] src/xxd/xxd.c
+ true
+ )
+
- name: Generate gcov files
if: matrix.coverage
run: |
diff --git a/runtime/tools/README.txt b/runtime/tools/README.txt
index 19976b325..1758ca653 100644
--- a/runtime/tools/README.txt
+++ b/runtime/tools/README.txt
@@ -16,6 +16,9 @@ pltags.pl: Perl script to create a tags file from Perl scripts.

ref: Shell script for the K command.

+preproc_indent.vim:
+ Fix preprocessor indentation in Vim's C source code.
+
shtags.*: Perl script to create a tags file from a shell script.

vim132: Shell script to edit in 132 column mode on vt100 compatible
diff --git a/runtime/tools/preproc_indent.vim b/runtime/tools/preproc_indent.vim
new file mode 100644
index 000000000..035ca0e24
--- /dev/null
+++ b/runtime/tools/preproc_indent.vim
@@ -0,0 +1,148 @@
+vim9script
+# Script to fix preprocessor indentation in Vim's C source code.
+#
+# Usage: Vim -S <this-file>
+#
+# Specifications:
+# - If there is no indentation on the line containing the preprocessor
+# directive (`#`) following the first `#if~`, the indentation amount is
+# `nesting level - 1` spaces. Otherwise, the indentation amount is `nesting
+# level` spaces.
+# - However, if a preprocessor directive line is detected after the
+# corresponding `#endif` of the above `#if~`, the indentation amount is
+# fixed at `nesting level` and the line is reprocessed from the first line.
+# - If the preprocessor directive line ends with a line continuation (`\`) and
+# the next line is blank, the line continuation (`\`) and the next line are
+# deleted.
+#
+# Author: Hirohito Higashi (@h-east)
+# Last Update: 2026 Jan 12
+
+def Get_C_source_files(): list<string>
+ var list_of_c_files: list<string> = []
+ if empty(list_of_c_files)
+ var fpath = '../../src'
+ var list = glob(fpath .. '/*.[ch]', 0, 1) + [fpath .. '/xxd/xxd.c']
+ # Some files are auto-generated, so skip those
+ list_of_c_files = filter(list, (i, v) => v !~ 'dlldata.c\|if_ole.h\|iid_ole.c')
+ endif
+ return list_of_c_files
+enddef
+
+def FixPreprocessorIndent(fname: string)
+ execute 'edit! ' .. fname
+
+ var nest: number = 0
+ var indent_offset: number = 0 # -1 if whole-file guard detected
+ var first_if_seen: bool = false
+ var offset_determined: bool = false
+ var whole_file_guard_ended = false
+
+ # First pass: remove trailing backslash + empty next line
+ var lnum = 1
+ while lnum <= line('$')
+ var line: string = getline(lnum)
+ if line =~# '^\s*#.*\$'
+ var next_line: string = getline(lnum + 1)
+ if next_line =~# '^\s*$'
+ # Remove backslash from current line and delete next line
+ setline(lnum, substitute(line, '\s*\$', '', ''))
+ deletebufline('%', lnum + 1)
+ continue # Don't increment, check same line again
+ endif
+ endif
+ lnum += 1
+ endwhile
+
+ # Second pass: fix preprocessor indent
+ while true
+ var is_reprocess: bool = false
+ for l in range(1, line('$'))
+ var line: string = getline(l)
+
+ # Skip if not a preprocessor directive
+ if line !~# '^\s*#'
+ continue
+ endif
+
+ # Extract directive and current indent
+ var match_li: list<string> = matchlist(line, '^\(\s*\)#\(\s*\)\(\w\+\)')
+ if empty(match_li)
+ continue
+ endif
+ var cur_spaces: string = !empty(match_li[1]) ? match_li[1] : match_li[2]
+ var directive: string = match_li[3]
+
+ # If indent_offset != 0 but we encounter indented #, it's not whole-file
+ # guard. Reprocess from line 1 with indent_offset=0
+ if whole_file_guard_ended && offset_determined && indent_offset != 0
+ indent_offset = 0
+ nest = 0
+ is_reprocess = true
+ break
+ endif
+
+ # After first #if, determine offset from first nested directive
+ # Only check if # is at column 1 (no leading spaces)
+ if first_if_seen && !offset_determined
+ offset_determined = true
+ if empty(cur_spaces)
+ # No indent after first `#if` --> whole-file guard style
+ indent_offset = -1
+ endif
+ endif
+
+ # Determine expected indent based on directive type
+ var expected_indent: number
+
+ if directive ==# 'if' || directive ==# 'ifdef' || directive ==# 'ifndef'
+ if !first_if_seen
+ first_if_seen = true
+ endif
+ expected_indent = nest + indent_offset
+ nest += 1
+ elseif directive ==# 'elif' || directive ==# 'else'
+ expected_indent = nest - 1 + indent_offset
+ elseif directive ==# 'endif'
+ nest -= 1
+ if nest <= 0
+ # Reset for next top-level block (but keep offset_determined)
+ nest = 0
+ whole_file_guard_ended = true
+ endif
+ expected_indent = nest + indent_offset
+ else
+ # Other directives (#define, #include, #error, #pragma, etc.)
+ expected_indent = nest + indent_offset
+ endif
+
+ if expected_indent < 0
+ expected_indent = 0
+ endif
+
+ # Build expected line
+ var rest = substitute(line, '^\s*#\s*', '', '')
+ var expected_line: string
+ expected_line = '#' .. repeat(' ', expected_indent) .. rest
+
+ # Update line if different
+ if line !=# expected_line
+ setline(l, expected_line)
+ endif
+ endfor
+
+ if !is_reprocess
+ break
+ endif
+ endwhile
+
+ update
+enddef
+
+# Main
+for fname in Get_C_source_files()
+ FixPreprocessorIndent(fname)
+endfor
+
+qall!
+# vim: et ts=2 sw=0