ninja backend: don't hide all compiler warnings for transpiled languages

This was originally added for vala only, with the rationale that vala
generates bad code that has warnings. Unfortunately, the rationale was
fatally flawed. The compiler warns about a number of things, which the
user can control depending on their code (or their code generator's
code), but some of those things are absolutely critical to warn about.

In particular, GCC 14 and clang 17 are updating their defaults to warn
-- and error by default for -- invalid C code that breaks the standard,
but has been silently accepted for over 20 years "because lots of people
do it". The code in question is UB, and compilers will generate faulty
machine code that behaves erroneously and probably has a mass of CVEs
waiting to happen.

Compiler warnings are NOT safe to just... universally turn off. Compiler
warnings could be either:

- coding style lints

- threatening statements that the code is factually and behaviorally wrong

There is no magic bullet to ignore the former while respecting the
latter. And the very last thing we should ever do is pass `-w`, since
that causes ALL warnings to be disabled, even the manually added
`-Werror=XXX`.

If vala generated code creates warnings, then the vala compiler can
decrease the log level by generating better code, or by adding warning
suppression pragmas for *specific* issues, such as unused functions.

4 files changed, 0 insertions, 29 deletions

diff --git a/test cases/failing build/1 vala c werror/meson.build b/test cases/failing build/1 vala c werror/meson.build
deleted file mode 100644
index 736d7aa..0000000
--- a/test cases/failing build/1 vala c werror/meson.build
+++ /dev/null
@@ -1,10 +0,0 @@
-project('valatest', 'c', default_options : 'werror=true')
-
-if find_program('valac', required : false).found()
-  add_languages('vala')
-  valadeps = [dependency('glib-2.0'), dependency('gobject-2.0')]
-  # Must fail due to -Werror and unused variable in C file
-  executable('valaprog', 'prog.vala', 'unused-var.c', dependencies : valadeps)
-else
-  executable('failprog', 'unused-var.c')
-endif
diff --git a/test cases/failing build/1 vala c werror/prog.vala b/test cases/failing build/1 vala c werror/prog.vala
deleted file mode 100644
index 638e776..0000000
--- a/test cases/failing build/1 vala c werror/prog.vala
+++ /dev/null
@@ -1,7 +0,0 @@
-class MainProg : GLib.Object {
-
-    public static int main(string[] args) {
-        stdout.printf("Vala is working.\n");
-        return 0;
-    }
-}
diff --git a/test cases/failing build/1 vala c werror/unused-var.c b/test cases/failing build/1 vala c werror/unused-var.c
deleted file mode 100644
index 6b85078..0000000
--- a/test cases/failing build/1 vala c werror/unused-var.c
+++ /dev/null
@@ -1,8 +0,0 @@
-#warning "something"
-
-int
-somelib(void)
-{
-  int unused_var;
-  return 33;
-}
diff --git a/test cases/vala/5 target glib/meson.build b/test cases/vala/5 target glib/meson.build
index f285d9f..089bb3c 100644
--- a/test cases/vala/5 target glib/meson.build
+++ b/test cases/vala/5 target glib/meson.build
@@ -1,9 +1,5 @@
 project('valatest', 'vala', 'c')
 
-if not meson.is_unity()
-  add_global_arguments('-Werror', language : 'c')
-endif
-
 valadeps = [dependency('glib-2.0', version : '>=2.32'), dependency('gobject-2.0')]
 
 e = executable('valaprog', 'GLib.Thread.vala', 'retcode.c', dependencies : valadeps)