options: add a deprecation warning printing mechanism

We have a warning mechanism for removed and for replaced options, but
none yet for options which have been simply deprecated.

For the following commit.

(Fun fact: just adding the m_option field increases binary size by
14KB.)

1 files changed, 7 insertions, 0 deletions

diff --git a/options/m_config.c b/options/m_config.c
index a3dcb30067..1cb01ebfdc 100644
--- a/options/m_config.c
+++ b/options/m_config.c
@@ -499,6 +499,13 @@ struct m_config_option *m_config_get_co(const struct m_config *config,
                     co->warning_was_printed = true;
                 }
                 return NULL;
+            } else if (co->opt->deprecation_message) {
+                if (!co->warning_was_printed) {
+                    MP_WARN(config, "Warning: option %s%s is deprecated "
+                            "and might be removed in the future (%s).\n",
+                            prefix, co->name, co->opt->deprecation_message);
+                    co->warning_was_printed = true;
+                }
             }
             return co;
         }