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.

vm:entry-pointDefining entry-points into Dart code for an embedder or native methods
vm:never-inlineNever inline a function or method
vm:prefer-inlineInline a function or method when possible
vm:notify-debugger-on-exceptionMarks 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-nameAllows 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.

vm:unsafe:no-interruptsRemoves 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.

vm:exact-result-typeDeclaring an exact result type of a method
vm:recognizedMarking 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.

vm:testing.unsafe.trace-entrypoints-fnObserving which flow-graph-level entry-point was used when a function was called