Merge pull request #9920 from 9999years/forbid-nested-debuggers

Forbid nested debuggers

(cherry picked from commit e164b39ee90fd655dbb7f479fdd4fbe38cc883bd)
Change-Id: Iff62f40fd251116516a63e2d3f9fb5b21480b16d
This commit is contained in:
Théophane Hufschmitt 2024-03-05 06:58:29 +01:00 committed by eldritch horrors
parent 45623f077f
commit 6c29016a09
7 changed files with 93 additions and 9 deletions

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@ -0,0 +1,32 @@
---
synopsis: Nested debuggers are no longer supported
prs: 9920
---
Previously, evaluating an expression that throws an error in the debugger would
enter a second, nested debugger:
```
nix-repl> builtins.throw "what"
error: what
Starting REPL to allow you to inspect the current state of the evaluator.
Welcome to Nix 2.18.1. Type :? for help.
nix-repl>
```
Now, it just prints the error message like `nix repl`:
```
nix-repl> builtins.throw "what"
error:
… while calling the 'throw' builtin
at «string»:1:1:
1| builtins.throw "what"
| ^
error: what
```

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@ -233,12 +233,6 @@ ReplExitStatus NixRepl::mainLoop()
printMsg(lvlError, e.msg());
}
} catch (EvalError & e) {
// in debugger mode, an EvalError should trigger another repl session.
// when that session returns the exception will land here. No need to show it again;
// show the error for this repl session instead.
if (state->debugRepl && !state->debugTraces.empty())
showDebugTrace(std::cout, state->positions, state->debugTraces.front());
else
printMsg(lvlError, e.msg());
} catch (Error & e) {
printMsg(lvlError, e.msg());

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@ -778,10 +778,24 @@ std::unique_ptr<ValMap> mapStaticEnvBindings(const SymbolTable & st, const Stati
return vm;
}
/**
* Sets `inDebugger` to true on construction and false on destruction.
*/
class DebuggerGuard {
bool & inDebugger;
public:
DebuggerGuard(bool & inDebugger) : inDebugger(inDebugger) {
inDebugger = true;
}
~DebuggerGuard() {
inDebugger = false;
}
};
void EvalState::runDebugRepl(const Error * error, const Env & env, const Expr & expr)
{
// double check we've got the debugRepl function pointer.
if (!debugRepl)
// Make sure we have a debugger to run and we're not already in a debugger.
if (!debugRepl || inDebugger)
return;
auto dts =
@ -808,6 +822,7 @@ void EvalState::runDebugRepl(const Error * error, const Env & env, const Expr &
auto se = getStaticEnv(expr);
if (se) {
auto vm = mapStaticEnvBindings(symbols, *se.get(), env);
DebuggerGuard _guard(inDebugger);
auto exitStatus = (debugRepl)(ref<EvalState>(shared_from_this()), *vm);
switch (exitStatus) {
case ReplExitStatus::QuitAll:

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@ -152,6 +152,7 @@ struct DebugTrace {
bool isError;
};
class EvalState : public std::enable_shared_from_this<EvalState>
{
public:
@ -210,6 +211,7 @@ public:
*/
ReplExitStatus (* debugRepl)(ref<EvalState> es, const ValMap & extraEnv);
bool debugStop;
bool inDebugger = false;
int trylevel;
std::list<DebugTrace> debugTraces;
std::map<const Expr*, const std::shared_ptr<const StaticEnv>> exprEnvs;

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@ -0,0 +1 @@
builtins.break {}

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@ -0,0 +1,39 @@
we enter a debugger via builtins.break in the input file.
info: breakpoint reached
causing another debugger even should not nest, but simply
print the error, skip the breakpoint, etc as appropriate.
nix-repl> "values show"
"values show"
nix-repl> builtins.break 2
2
nix-repl> builtins.throw "foo"
error:
… while calling the 'throw' builtin
at «string»:1:1:
1| builtins.throw "foo"
| ^
error: foo
nix-repl> assert false; 2
error: assertion 'false' failed
at «string»:1:1:
1| assert false; 2
| ^
exiting the debug frame should allow another to open.
nix-repl> :c
nix-repl> builtins.throw "bar"
error: bar
and once again, more breakpoints are ignored.
nix-repl> builtins.break 3
3

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@ -126,5 +126,6 @@ DEBUGGER_TEST(regression_9918);
DEBUGGER_TEST(regression_9917);
DEBUGGER_TEST(regression_l145);
DEBUGGER_TEST(stack_vars);
DEBUGGER_TEST(no_nested_debuggers);
};