Fix compile error for non-void-returning inplace_functions

The error occurs when testing for or calling an unassigned function.
PaulStoffregen · Sep 2, 2023 · 33ed570 · 33ed570
1 parent 6d091ca
commit 33ed570
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diff --git a/teensy3/inplace_function.h b/teensy3/inplace_function.h
@@ -1,9 +1,4 @@
-#pragma once
-
 // https://github.com/WG21-SG14/SG14/blob/master/SG14/inplace_function.h
-//
-// For use with Teensy, allow uninitialized to be no-operation without error
-#define SG14_INPLACE_FUNCTION_THROW(x)
 
 /*
  * Boost Software License - Version 1.0 - August 17th, 2003
@@ -31,13 +26,21 @@
  * DEALINGS IN THE SOFTWARE.
  */
 
+#pragma once
+
 #include <type_traits>
 #include <utility>
 #include <functional>
 #include <cstddef>
 
+// Teensy doesn't support runtime exceptions, so calling an uninitialized
+// inplace_function needs to call a non-returning function. We can't do nothing
+// because that would cause a compile error for non-void-returning functions.
+// Additionally, we can't return some default value because that's not possible
+// for return types that have a non-trivial constructor.
+// See 'invoke_ptr' initialization in 'vtable()' constructor.
 #ifndef SG14_INPLACE_FUNCTION_THROW
-#define SG14_INPLACE_FUNCTION_THROW(x) throw (x)
+#define SG14_INPLACE_FUNCTION_THROW(x) std::__throw_bad_function_call()
 #endif
 
 namespace stdext {

diff --git a/teensy4/inplace_function.h b/teensy4/inplace_function.h
@@ -1,9 +1,4 @@
-#pragma once
-
 // https://github.com/WG21-SG14/SG14/blob/master/SG14/inplace_function.h
-//
-// For use with Teensy, allow uninitialized to be no-operation without error
-#define SG14_INPLACE_FUNCTION_THROW(x)
 
 /*
  * Boost Software License - Version 1.0 - August 17th, 2003
@@ -31,13 +26,21 @@
  * DEALINGS IN THE SOFTWARE.
  */
 
+#pragma once
+
 #include <type_traits>
 #include <utility>
 #include <functional>
 #include <cstddef>
 
+// Teensy doesn't support runtime exceptions, so calling an uninitialized
+// inplace_function needs to call a non-returning function. We can't do nothing
+// because that would cause a compile error for non-void-returning functions.
+// Additionally, we can't return some default value because that's not possible
+// for return types that have a non-trivial constructor.
+// See 'invoke_ptr' initialization in 'vtable()' constructor.
 #ifndef SG14_INPLACE_FUNCTION_THROW
-#define SG14_INPLACE_FUNCTION_THROW(x) throw (x)
+#define SG14_INPLACE_FUNCTION_THROW(x) std::__throw_bad_function_call()
 #endif
 
 namespace stdext {