Alexander Markov
0e5a539315
Flutter in google3 uses --delete-tostring-package-uri compiler option
to remove toString methods in package:flutter and dart:ui to reduce
size in release mode.
This has unfortunate effect of removing toString methods from exception
classes which may provide valuable information for investigating
problems seen in the wild.
This change adds a new @pragma('flutter:keep-to-string-in-subtypes')
on classes to keep toString methods on all subtypes of the annotated
classes. This pragma is now used on Exception and Error classes in
dart:core.
TEST=pkg/vm/test/transformations/to_string_transformer_test.dart
Issue: https://github.com/flutter/flutter/issues/61562
Change-Id: Ib739c83cdf6b539208f705ba198e63b8bc54fa61
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/227920
Reviewed-by: Dan Field <dnfield@google.com>
Reviewed-by: Slava Egorov <vegorov@google.com>
Commit-Queue: Alexander Markov <alexmarkov@google.com>
3.5 KiB
VM-Specific Pragma Annotations
Pragmas for general use
These pragmas are part of the VM's API and are safe for use in external code.
| Pragma | Meaning |
|---|---|
vm:entry-point |
Defining entry-points into Dart code for an embedder or native methods |
vm:never-inline |
Never inline a function or method |
vm:prefer-inline |
Inline a function or method when possible |
vm:notify-debugger-on-exception |
Marks a function that catches exceptions, making the VM treat any caught exception as if they were uncaught. This can be used to notify an attached debugger during debugging, without pausing the app during regular execution. |
vm:external-name |
Allows to specify an external (native) name for an external function. This name is used to lookup native implementation via native resolver associated with the current library through embedding APIs. This is a replacement for legacy VM specific native "name" syntax. |
Unsafe pragmas for general use
These pragmas are available for use in third-party code but are potentially unsafe. The use of these pragmas is discouraged unless the developer fully understands potential repercussions.
| Pragma | Meaning |
|---|---|
vm:unsafe:no-interrupts |
Removes all CheckStackOverflow instructions from the optimized version of the marked function, which disables stack overflow checking and interruption within that function. This pragma exists mainly for performance evaluation and should not be used in a general-purpose code, because VM relies on these checks for OOB message delivery and GC scheduling. |
Pragmas for internal use
These pragmas can cause unsound behavior if used incorrectly and therefore are only allowed within the core SDK libraries.
| Pragma | Meaning |
|---|---|
vm:exact-result-type |
Declaring an exact result type of a method |
vm:recognized |
Marking this as a recognized method |
Pragmas for internal testing
These pragmas are used for inspecting or modifying internal VM state and should be used exclusively by SDK tests.
They must be enabled with the --enable-testing-pragmas flag.
The names of these pragmas are prefixed with "testing".
Additionally, they are categorized into "safe" and "unsafe" forms: "safe" pragmas should not affect the behavior of the program and can be safely added anywhere, whereas "unsafe" pragmas may change the code's behavior or may cause the VM to crash if used improperly.
| Pragma | Meaning |
|---|---|
vm:testing.unsafe.trace-entrypoints-fn |
Observing which flow-graph-level entry-point was used when a function was called |
Flutter toString transformer pragmas
These pragmas are useful to exclude certain toString methods from toString transformation,
which is enabled with --delete-tostring-package-uri option in kernel compilers and
used by Flutter to remove certain toString methods in release mode to reduce size.
| Pragma | Meaning |
|---|---|
flutter:keep-to-string |
Avoid transforming the annotated toString method. |
flutter:keep-to-string-in-subtypes |
Avoid transforming toString methods in all subtypes of the annotated class. |