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compiler: properly process defer in conditional statements

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Signed-off-by: Evgeniy Stratonikov <evgeniy@nspcc.ru>
This commit is contained in:
Evgeniy Stratonikov 2022-02-03 13:20:40 +03:00
parent 10d006195a
commit b5afe24090
3 changed files with 104 additions and 3 deletions
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18
pkg/compiler/codegen.go
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@ -1024,10 +1024,14 @@ func (c *codegen) Visit(node ast.Node) ast.Visitor {
binary.LittleEndian.PutUint16(param[0:], catch)
binary.LittleEndian.PutUint16(param[4:], finally)
emit.Instruction(c.prog.BinWriter, opcode.TRYL, param)
index := c.scope.newLocal(fmt.Sprintf("defer@%d", n.Call.Pos()))
emit.Opcodes(c.prog.BinWriter, opcode.PUSH1)
c.emitStoreByIndex(varLocal, index)
c.scope.deferStack = append(c.scope.deferStack, deferInfo{
catchLabel: catch,
finallyLabel: finally,
expr: n.Call,
localIndex: index,
})
return nil
@ -1330,13 +1334,21 @@ func (c *codegen) isCallExprSyscall(e ast.Expr) bool {
// 2. `recover` can or can not handle a possible exception.
// Thus we use the following approach:
// 1. Throwed exception is saved in a static field X, static fields Y and is set to true.
// 2. CATCH and FINALLY blocks are the same, and both contain the same CALLs.
// 3. In CATCH block we set Y to true and emit default return values if it is the last defer.
// 4. Execute FINALLY block only if Y is false.
// 2. For each defer local there is a dedicated local variable which is set to 1 if `defer` statement
// is encountered during an actual execution.
// 3. CATCH and FINALLY blocks are the same, and both contain the same CALLs.
// 4. Right before the CATCH block check a variable from (2). If it is null, jump to the end of CATCH+FINALLY block.
// 5. In CATCH block we set Y to true and emit default return values if it is the last defer.
// 6. Execute FINALLY block only if Y is false.
func (c *codegen) processDefers() {
for i := len(c.scope.deferStack) - 1; i >= 0; i-- {
stmt := c.scope.deferStack[i]
after := c.newLabel()
c.emitLoadByIndex(varLocal, c.scope.deferStack[i].localIndex)
emit.Opcodes(c.prog.BinWriter, opcode.ISNULL)
emit.Jmp(c.prog.BinWriter, opcode.JMPIFL, after)
emit.Jmp(c.prog.BinWriter, opcode.ENDTRYL, after)
c.setLabel(stmt.catchLabel)