package interp

import "golang.org/x/tools/go/ssa/interp"

Package ssa/interp defines an interpreter for the SSA representation of Go programs.

This interpreter is provided as an adjunct for testing the SSA construction algorithm. Its purpose is to provide a minimal metacircular implementation of the dynamic semantics of each SSA instruction. It is not, and will never be, a production-quality Go interpreter.

The following is a partial list of Go features that are currently unsupported or incomplete in the interpreter.

* Unsafe operations, including all uses of unsafe.Pointer, are impossible to support given the "boxed" value representation we have chosen.

* The reflect package is only partially implemented.

* The "testing" package is no longer supported because it depends on low-level details that change too often.

* "sync/atomic" operations are not atomic due to the "boxed" value representation: it is not possible to read, modify and write an interface value atomically. As a consequence, Mutexes are currently broken.

* recover is only partially implemented. Also, the interpreter makes no attempt to distinguish target panics from interpreter crashes.

* the sizes of the int, uint and uintptr types in the target program are assumed to be the same as those of the interpreter itself.

* all values occupy space, even those of types defined by the spec to have zero size, e.g. struct{}. This can cause asymptotic performance degradation.

* os.Exit is implemented using panic, causing deferred functions to run.

Index ¶

• Variables
• func Interpret(mainpkg *ssa.Package, mode Mode, sizes types.Sizes, filename string, args []string) (exitCode int)
• type Mode

Variables ¶

var CapturedOutput *bytes.Buffer

This variable is no longer used but remains to prevent build breakage.

Functions ¶

func Interpret ¶

func Interpret(mainpkg *ssa.Package, mode Mode, sizes types.Sizes, filename string, args []string) (exitCode int)

Interpret interprets the Go program whose main package is mainpkg. mode specifies various interpreter options. filename and args are the initial values of os.Args for the target program. sizes is the effective type-sizing function for this program.

Interpret returns the exit code of the program: 2 for panic (like gc does), or the argument to os.Exit for normal termination.

The SSA program must include the "runtime" package.

Type parameterized functions must have been built with InstantiateGenerics in the ssa.BuilderMode to be interpreted.

Types ¶

type Mode ¶

type Mode uint

Mode is a bitmask of options affecting the interpreter.

const (
	DisableRecover Mode = 1 << iota // Disable recover() in target programs; show interpreter crash instead.
	EnableTracing                   // Print a trace of all instructions as they are interpreted.
)

Source Files ¶

external.go interp.go map.go ops.go reflect.go value.go