ConfigToolDependency: Don't fallback to system tool when cross compiling

The system tool is always the wrong thing to use and cause hard to debug
issues when trying to link system libraries with cross built binaries.

The ExternalDependency base class already had a method to deal with
this, used by PkgConfigDependency and QtBaseDependency, so it should
make things more consistent.

4 files changed, 15 insertions, 22 deletions

diff --git a/docs/markdown/Dependencies.md b/docs/markdown/Dependencies.md
index 17c9991..572a3d1 100644
--- a/docs/markdown/Dependencies.md
+++ b/docs/markdown/Dependencies.md
@@ -242,6 +242,9 @@ libgcrypt_dep = dependency('libgcrypt', version: '>= 1.8')
 gpgme_dep = dependency('gpgme', version: '>= 1.0')
 ```
 
+*Since 0.55.0* Meson won't search $PATH any more for a config tool binary when
+cross compiling if the config tool did not have an entry in the cross file.
+
 ## AppleFrameworks
 
 Use the `modules` keyword to list frameworks required, e.g.
diff --git a/docs/markdown/snippets/config_tool_no_cross_path.md b/docs/markdown/snippets/config_tool_no_cross_path.md
new file mode 100644
index 0000000..cec22e4
--- /dev/null
+++ b/docs/markdown/snippets/config_tool_no_cross_path.md
@@ -0,0 +1,7 @@
+## Config tool based dependencies no longer search PATH for cross compiling
+
+Before 0.55.0 config tool based dependencies (llvm-config, cups-config, etc),
+would search system $PATH if they weren't defined in the cross file. This has
+been a source of bugs and has been deprecated. It is now removed, config tool
+binaries must be specified in the cross file now or the dependency will not
+be found.
diff --git a/mesonbuild/dependencies/base.py b/mesonbuild/dependencies/base.py
index 95a3956..bcb1531 100644
--- a/mesonbuild/dependencies/base.py
+++ b/mesonbuild/dependencies/base.py
@@ -437,28 +437,11 @@ class ConfigToolDependency(ExternalDependency):
         """
         if not isinstance(versions, list) and versions is not None:
             versions = listify(versions)
-
-        tool = self.env.lookup_binary_entry(self.for_machine, self.tool_name)
-        if tool is not None:
-            tools = [tool]
-        else:
-            if not self.env.machines.matches_build_machine(self.for_machine):
-                mlog.deprecation('No entry for {0} specified in your cross file. '
-                                 'Falling back to searching PATH. This may find a '
-                                 'native version of {0}! This will become a hard '
-                                 'error in a future version of meson'.format(self.tool_name))
-            tools = [[t] for t in self.tools]
-
         best_match = (None, None)
-        for tool in tools:
-            if len(tool) == 1:
-                # In some situations the command can't be directly executed.
-                # For example Shell scripts need to be called through sh on
-                # Windows (see issue #1423).
-                potential_bin = ExternalProgram(tool[0], silent=True)
-                if not potential_bin.found():
-                    continue
-                tool = potential_bin.get_command()
+        for potential_bin in self.search_tool(self.tool_name, self.tool_name, self.tools):
+            if not potential_bin.found():
+                continue
+            tool = potential_bin.get_command()
             try:
                 p, out = Popen_safe(tool + [self.version_arg])[:2]
             except (FileNotFoundError, PermissionError):
diff --git a/test cases/frameworks/21 libwmf/meson.build b/test cases/frameworks/21 libwmf/meson.build
index 6952bf7..9dbab6a 100644
--- a/test cases/frameworks/21 libwmf/meson.build
+++ b/test cases/frameworks/21 libwmf/meson.build
@@ -1,7 +1,7 @@
 project('libwmf test', 'c')
 
 wm = find_program('libwmf-config', required : false)
-if not wm.found()
+if not wm.found() or meson.is_cross_build()
   error('MESON_SKIP_TEST: libwmf-config not installed')
 endif