Merge pull request #4064 from weiznich/fix/mysqlclient_regression_with_old_versions

weiznich · weiznich · commit 48ccc7804c7e · 2024-06-12T13:21:27.000+02:00
Fix a potential regression with old mysqlclient-sys versions
diff --git a/diesel/src/mysql/connection/bind.rs b/diesel/src/mysql/connection/bind.rs
@@ -389,13 +389,13 @@ impl BindData {
             length,
             capacity,
             flags,
-            is_null: ffi::FALSE,
-            is_truncated: Some(ffi::FALSE),
+            is_null: super::raw::ffi_false(),
+            is_truncated: Some(super::raw::ffi_false()),
         }
     }
 
     fn is_truncated(&self) -> bool {
-        self.is_truncated.unwrap_or(ffi::FALSE) != ffi::FALSE
+        self.is_truncated.unwrap_or(super::raw::ffi_false()) != super::raw::ffi_false()
     }
 
     fn is_fixed_size_buffer(&self) -> bool {
@@ -711,7 +711,9 @@ impl From<(ffi::enum_field_types, Flags)> for MysqlType {
                  something has gone wrong. Please open an issue at \
                  the diesel github repo."
             ),
-
+            // depending on the bindings version
+            // there might be no unlisted field type
+            #[allow(unreachable_patterns)]
             t => unreachable!(
                 "Unsupported type encountered: {t:?}. \
                  If you ever see this error, something has gone wrong. \
diff --git a/diesel/src/mysql/connection/raw.rs b/diesel/src/mysql/connection/raw.rs
@@ -11,6 +11,19 @@ use crate::result::{ConnectionError, ConnectionResult, QueryResult};
 
 pub(super) struct RawConnection(NonNull<ffi::MYSQL>);
 
+// old versions of mysqlclient do not expose
+// ffi::FALSE, so we need to have our own compatibility
+// wrapper here
+//
+// Depending on the bindings version ffi::my_bool
+// might be an actual bool or a i8. For the former
+// case `default()` corresponds to `false` for the later
+// to `0` which is both interpreted as false
+#[inline(always)]
+pub(super) fn ffi_false() -> ffi::my_bool {
+    Default::default()
+}
+
 impl RawConnection {
     pub(super) fn new() -> Self {
         perform_thread_unsafe_library_initialization();
@@ -175,7 +188,7 @@ impl RawConnection {
     }
 
     fn more_results(&self) -> bool {
-        unsafe { ffi::mysql_more_results(self.0.as_ptr()) != ffi::FALSE }
+        unsafe { ffi::mysql_more_results(self.0.as_ptr()) != ffi_false() }
     }
 
     fn next_result(&self) -> QueryResult<()> {
