utmp: rewrite utmp logging

This patch generalizes the utmp support, to not only support
libutempter, but also ulog (and in the future, even more interfaces).

* Rename config option main.utempter to main.utmp-helper
* Add meson option -Dutmp-backend=none|libutempter|ulog|auto
* Rename meson option -Ddefault-utempter-path to -Dutmp-default-helper-path
* utmp is no longer detected at compile time, but at runtime instead.

Meson will configure the following pre-processor macros, based on the
selected utmp backend:

* UTMP_ADD - argument to pass to utmp helper when adding a record (starting foot)
* UTMP_DEL - argument to pass to utmp helper when removing a record (exiting foot)
* UTMP_DEL_HAVE_ARGUMENT - if defined, UTMP_DEL expects an extra argument ($WAYLAND_DISPLAY)
* UTMP_DEFAULT_HELPER_PATH - path to the default utmp helper binary

The documentation has been updated to mention which arguments are
passed to the helper binary.

Closes #1314

CHANGELOG.md

@@ -46,6 +46,9 @@
 ### Added
 
 * VT: implemented `XTQMODKEYS` query (`CSI ? Pp m`).
+* Meson option `utmp-backend=none|libutempter|ulog|auto`. The default
+  is `auto`, which will select `libutempter` on Linux, `ulog` on
+  FreeBSD, and `none` for all others.
 
 
 ### Changed
@@ -54,9 +57,17 @@
   `CSI R`. The kitty keyboard protocol originally allowed F3 to be
   encoded as `CSI R`, but this was removed from the specification
   since `CSI R` conflicts with the _”Cursor Position Report”_.
+* `[main].utempter` renamed to `[main].utmp-helper`. The old option
+  name is still recognized, but will log a deprecation warning.
+* Meson option `default-utempter-path` renamed to
+  `utmp-default-helper-path`.
 
 
 ### Deprecated
+
+* `[main].utempter` option.
+
+
 ### Removed
 ### Fixed
 

INSTALL.md

@@ -45,7 +45,8 @@ subprojects.
 * wayland (_client_ and _cursor_ libraries)
 * xkbcommon
 * utf8proc (_optional_, needed for grapheme clustering)
-* libutempter (_optional_, needed for utmp logging)
+* libutempter (_optional_, needed for utmp logging on Linux)
+* ulog (_optional_, needed for utmp logging on FreeBSD)
 * [fcft](https://codeberg.org/dnkl/fcft) [^1]
 
 [^1]: can also be built as subprojects, in which case they are
@@ -142,17 +143,18 @@ mkdir -p bld/release && cd bld/release
 
 Available compile-time options:
 
-| Option                               | Type    | Default                 | Description                                               | Extra dependencies |
+| Option                               | Type    | Default                 | Description                                                                     | Extra dependencies  |
-|--------------------------------------|---------|-------------------------|-----------------------------------------------------------|--------------------|
+|--------------------------------------|---------|-------------------------|---------------------------------------------------------------------------------|---------------------|
-| `-Ddocs`                             | feature | `auto`                  | Builds and install documentation                          | scdoc              |
+| `-Ddocs`                             | feature | `auto`                  | Builds and install documentation                                                | scdoc               |
-| `-Dtests`                            | bool    | `true`                  | Build tests (adds a `ninja test` build target)            | none               |
+| `-Dtests`                            | bool    | `true`                  | Build tests (adds a `ninja test` build target)                                  | None                |
-| `-Dime`                              | bool    | `true`                  | Enables IME support                                       | None               |
+| `-Dime`                              | bool    | `true`                  | Enables IME support                                                             | None                |
-| `-Dgrapheme-clustering`              | feature | `auto`                  | Enables grapheme clustering                               | libutf8proc        |
+| `-Dgrapheme-clustering`              | feature | `auto`                  | Enables grapheme clustering                                                     | libutf8proc         |
-| `-Dterminfo`                         | feature | `enabled`               | Build and install terminfo files                          | tic (ncurses)      |
+| `-Dterminfo`                         | feature | `enabled`               | Build and install terminfo files                                                | tic (ncurses)       |
-| `-Ddefault-terminfo`                 | string  | `foot`                  | Default value of `TERM`                                   | none               |
+| `-Ddefault-terminfo`                 | string  | `foot`                  | Default value of `TERM`                                                         | None                |
-| `-Dcustom-terminfo-install-location` | string  | `${datadir}/terminfo`   | Value to set `TERMINFO` to                                | None               |
+| `-Dcustom-terminfo-install-location` | string  | `${datadir}/terminfo`   | Value to set `TERMINFO` to                                                      | None                |
-| `-Dsystemd-units-dir`                | string  | `${systemduserunitdir}` | Where to install the systemd service files (absolute)     | None               |
+| `-Dsystemd-units-dir`                | string  | `${systemduserunitdir}` | Where to install the systemd service files (absolute)                           | None                |
-| `-Ddefault-utempter-path`            | feature | `auto`                  | Default path to utempter binary (‘none’ disables default) | libutempter        |
+| `-Dutmp-backend`                     | combo   | `auto`                  | Which utmp backend to use (`none`, `libutempter`, `ulog` or `auto`)             | libutempter or ulog |
+| `-Dutmp-default-helper-path`         | string  | `auto`                  | Default path to utmp helper binary. `auto` selects path based on `utmp-backend` | None                |
 
 Documentation includes the man pages, readme, changelog and license
 files.

config.c

@@ -1009,13 +1009,29 @@ parse_section_main(struct context *ctx)
     else if (strcmp(key, "box-drawings-uses-font-glyphs") == 0)
         return value_to_bool(ctx, &conf->box_drawings_uses_font_glyphs);
 
-    else if (strcmp(key, "utempter") == 0) {
+    else if (strcmp(key, "utmp-helper") == 0 || strcmp(key, "utempter") == 0) {
-        if (!value_to_str(ctx, &conf->utempter_path))
+        if (strcmp(key, "utempter") == 0) {
+            struct user_notification deprecation = {
+                .kind = USER_NOTIFICATION_DEPRECATED,
+                .text = xasprintf(
+                    "%s:%d: \033[1m[main].utempter\033[22m, "
+                    "use \033[1m[main].utmp-helper\033[22m instead",
+                    ctx->path, ctx->lineno),
+            };
+            tll_push_back(conf->notifications, deprecation);
+
+            LOG_WARN(
+                "%s:%d: [main].utempter is deprecated, "
+                "use [main].utmp-helper instead",
+                ctx->path, ctx->lineno);
+        }
+
+        if (!value_to_str(ctx, &conf->utmp_helper_path))
             return false;
 
-        if (strcmp(conf->utempter_path, "none") == 0) {
+        if (strcmp(conf->utmp_helper_path, "none") == 0) {
-            free(conf->utempter_path);
+            free(conf->utmp_helper_path);
-            conf->utempter_path = NULL;
+            conf->utmp_helper_path = NULL;
         }
 
         return true;
@@ -3019,9 +3035,12 @@ config_load(struct config *conf, const char *conf_path,
         },
 
         .env_vars = tll_init(),
-        .utempter_path = (strlen(FOOT_DEFAULT_UTEMPTER_PATH) > 0
+#if defined(UTMP_DEFAULT_HELPER_PATH)
-                          ? xstrdup(FOOT_DEFAULT_UTEMPTER_PATH)
+        .utmp_helper_path = ((strlen(UTMP_DEFAULT_HELPER_PATH) > 0 &&
-                          : NULL),
+                              access(UTMP_DEFAULT_HELPER_PATH, X_OK) == 0)
+                             ? xstrdup(UTMP_DEFAULT_HELPER_PATH)
+                             : NULL),
+#endif
         .notifications = tll_init(),
     };
 
@@ -3310,8 +3329,8 @@ config_clone(const struct config *old)
         tll_push_back(conf->env_vars, copy);
     }
 
-    conf->utempter_path =
+    conf->utmp_helper_path =
-        old->utempter_path != NULL ? xstrdup(old->utempter_path) : NULL;
+        old->utmp_helper_path != NULL ? xstrdup(old->utmp_helper_path) : NULL;
 
     conf->notifications.length = 0;
     conf->notifications.head = conf->notifications.tail = 0;
@@ -3379,7 +3398,7 @@ config_free(struct config *conf)
         tll_remove(conf->env_vars, it);
     }
 
-    free(conf->utempter_path);
+    free(conf->utmp_helper_path);
     user_notifications_free(&conf->notifications);
 }
 

config.h

@@ -320,7 +320,7 @@ struct config {
 
     env_var_list_t env_vars;
 
-    char *utempter_path;
+    char *utmp_helper_path;
 
     struct {
         enum fcft_scaling_filter fcft_filter;

doc/foot.ini.5.scd

@@ -343,9 +343,24 @@ empty string to be set, but it must be quoted: *KEY=""*)
 	(including SMT). Note that this is not always the best value. In
 	some cases, the number of physical _cores_ is better.
 
-*utempter*
+*utmp-helper*
-	Path to utempter helper binary. Set to *none* to disable utmp
+	Path to utmp logging helper binary.
-	records. Default: _@utempter@_.
+	
+	When starting foot, an utmp record is created by launching the
+	helper binary with the following arguments:
+	
+	```
+	@utmp_add_args@
+	```
+	
+	When foot is closed, the utmp record is removed by launching the
+	helper binary with the following arguments:
+	
+	```
+	@utmp_del_args@
+	```
+	
+	Set to *none* to disable utmp records. Default: _@utmp_helper_path@_.
 
 # SECTION: environment
 

doc/meson.build

@@ -2,16 +2,26 @@ sh = find_program('sh', native: true)
 
 scdoc_prog = find_program(scdoc.get_variable('scdoc'), native: true)
 
-if utempter_path == ''
+if utmp_backend != 'none'
-  default_utempter_value = 'not set'
+  utmp_add_args = '@0@ $WAYLAND_DISPLAY'.format(utmp_add)
+  utmp_del_args = (utmp_del_have_argument
+                   ? '@0@ $WAYLAND_DISPLAY'.format(utmp_del)
+                   : '@0@'.format(utmp_del))
+  utmp_path = utmp_default_helper_path
 else
-  default_utempter_value = utempter_path
+  utmp_add_args = '<no utmp support in foot>'
+  utmp_del_args = '<no utmp support in foot>'
+  utmp_path = 'none'
 endif
 
+
 conf_data = configuration_data(
   {
     'default_terminfo': get_option('default-terminfo'),
-    'utempter': default_utempter_value,
+    'utmp_backend': utmp_backend,
+    'utmp_add_args': utmp_add_args,
+    'utmp_del_args': utmp_del_args,
+    'utmp_helper_path': utmp_path,
   }
 )
 

foot.ini

@@ -34,7 +34,8 @@
 # word-delimiters=,│`|:"'()[]{}<>
 # selection-target=primary
 # workers=<number of logical CPUs>
-# utempter=/usr/lib/utempter/utempter
+# utmp-helper=/usr/lib/utempter/utempter  # When utmp backend is ‘libutempter’ (Linux)
+# utmp-helper=/usr/libexec/ulog-helper    # When utmp backend is ‘ulog’ (FreeBSD)
 
 [environment]
 # name=value

meson.build

@@ -16,30 +16,54 @@ if cc.has_function('memfd_create')
   add_project_arguments('-DMEMFD_CREATE', language: 'c')
 endif
 
-utempter_path = get_option('default-utempter-path')
+utmp_backend = get_option('utmp-backend')
-if utempter_path == ''
+if utmp_backend == 'auto'
-  utempter = find_program(
+  host_os = host_machine.system()
-    'utempter',
+  if host_os == 'linux'
-    required: false,
+    utmp_backend = 'libutempter'
-    dirs: [join_paths(get_option('prefix'), get_option('libdir'), 'utempter'),
+  elif host_os == 'freebsd'
-           join_paths(get_option('prefix'), get_option('libexecdir'), 'utempter'),
+    utmp_backend = 'ulog'
-           '/usr/lib/utempter',
-           '/usr/libexec/utempter',
-           '/lib/utempter']
-  )
-  if utempter.found()
-    utempter_path = utempter.full_path()
   else
-    utempter_path = ''
+    utmp_backend = 'none'
   endif
-elif utempter_path == 'none'
+endif
-  utempter_path = ''
+
+utmp_default_helper_path = get_option('utmp-default-helper-path')
+
+if utmp_backend == 'none'
+  utmp_add = ''
+  utmp_del = ''
+  utmp_del_have_argument = false
+  utmp_default_helper_path = ''
+elif utmp_backend == 'libutempter'
+  utmp_add = 'add'
+  utmp_del = 'del'
+  utmp_del_have_argument = true
+  if utmp_default_helper_path == 'auto'
+    utmp_default_helper_path = join_paths('/usr', get_option('libdir'), 'utempter', 'utempter')
+  endif
+elif utmp_backend == 'ulog'
+  utmp_add = 'login'
+  utmp_del = 'logout'
+  utmp_del_have_argument = false
+  if utmp_default_helper_path == 'auto'
+    utmp_default_helper_path = join_paths('/usr', get_option('libexecdir'), 'ulog-helper')
+  endif
+else
+    error('invalid utmp backend')
 endif
 
 add_project_arguments(
   ['-D_GNU_SOURCE=200809L',
-   '-DFOOT_DEFAULT_TERM="@0@"'.format(get_option('default-terminfo')),
+   '-DFOOT_DEFAULT_TERM="@0@"'.format(get_option('default-terminfo'))] +
-   '-DFOOT_DEFAULT_UTEMPTER_PATH="@0@"'.format(utempter_path)] +
+  (utmp_backend != 'none'
+  ? ['-DUTMP_ADD="@0@"'.format(utmp_add),
+     '-DUTMP_DEL="@0@"'.format(utmp_del),
+     '-DUTMP_DEFAULT_HELPER_PATH="@0@"'.format(utmp_default_helper_path)]
+  : []) +
+  (utmp_del_have_argument
+   ? ['-DUTMP_DEL_HAVE_ARGUMENT=1']
+   : []) +
   (is_debug_build
     ? ['-D_DEBUG']
    : [cc.get_supported_arguments('-fno-asynchronous-unwind-tables')]) +
@@ -343,7 +367,8 @@ summary(
     'Themes': get_option('themes'),
     'IME': get_option('ime'),
     'Grapheme clustering': utf8proc.found(),
-    'Utempter path': utempter_path,
+    'utmp backend': utmp_backend,
+    'utmp helper default path': utmp_default_helper_path,
     'Build terminfo': tic.found(),
     'Terminfo install location': terminfo_install_location,
     'Default TERM': get_option('default-terminfo'),

meson_options.txt

@@ -22,5 +22,7 @@ option('custom-terminfo-install-location', type: 'string', value: '',
 option('systemd-units-dir', type: 'string', value: '',
       description: 'Where to install the systemd service files (absolute path). Default: ${systemduserunitdir}')
 
-option('default-utempter-path', type: 'string', value: '',
+option('utmp-backend', type: 'combo', value: 'auto', choices: ['none', 'libutempter', 'ulog', 'auto'],
-       description: 'Default path to utempter helper binary. Default: auto-detect')
+       description: 'Which utmp logging backend to use. This affects how (with what arguments) the utmp helper binary (see \utmp-default-helper-path\')is called. Default: auto (linux=libutempter, freebsd=ulog, others=none)')
+option('utmp-default-helper-path', type: 'string', value: 'auto',
+       description: 'Default path to the utmp helper binary. Default: auto-detect')

terminal.c

@@ -207,25 +207,41 @@ fdm_ptmx_out(struct fdm *fdm, int fd, int events, void *data)
 static bool
 add_utmp_record(const struct config *conf, struct reaper *reaper, int ptmx)
 {
+#if defined(UTMP_ADD)
     if (ptmx < 0)
         return true;
-    if (conf->utempter_path == NULL)
+    if (conf->utmp_helper_path == NULL)
         return true;
 
-    char *const argv[] = {conf->utempter_path, "add", getenv("WAYLAND_DISPLAY"), NULL};
+    char *const argv[] = {conf->utmp_helper_path, UTMP_ADD, getenv("WAYLAND_DISPLAY"), NULL};
     return spawn(reaper, NULL, argv, ptmx, ptmx, -1, NULL);
+#else
+    return true;
+#endif
 }
 
 static bool
 del_utmp_record(const struct config *conf, struct reaper *reaper, int ptmx)
 {
+#if defined(UTMP_DEL)
     if (ptmx < 0)
         return true;
-    if (conf->utempter_path == NULL)
+    if (conf->utmp_helper_path == NULL)
         return true;
 
-    char *const argv[] = {conf->utempter_path, "del", getenv("WAYLAND_DISPLAY"), NULL};
+    char *del_argument =
+#if defined(UTMP_DEL_HAVE_ARGUMENT)
+        getenv("WAYLAND_DISPLAY")
+#else
+        NULL
+#endif
+        ;
+
+    char *const argv[] = {conf->utmp_helper_path, UTMP_DEL, del_argument, NULL};
     return spawn(reaper, NULL, argv, ptmx, ptmx, -1, NULL);
+#else
+    return true;
+#endif
 }
 
 #if PTMX_TIMING

tests/test-config.c

@@ -458,7 +458,7 @@ test_section_main(void)
     test_string(&ctx, &parse_section_main, "shell", &conf.shell);
     test_string(&ctx, &parse_section_main, "term", &conf.term);
     test_string(&ctx, &parse_section_main, "app-id", &conf.app_id);
-    test_string(&ctx, &parse_section_main, "utempter", &conf.utempter_path);
+    test_string(&ctx, &parse_section_main, "utempter", &conf.utmp_helper_path);
 
     test_c32string(&ctx, &parse_section_main, "word-delimiters", &conf.word_delimiters);