src/developer/debug/zxdb/console/commands/verb_steps.cc

// Copyright 2019 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "src/developer/debug/zxdb/console/commands/verb_steps.h"

#include "src/developer/debug/zxdb/client/frame.h"
#include "src/developer/debug/zxdb/client/process.h"
#include "src/developer/debug/zxdb/client/step_into_specific_thread_controller.h"
#include "src/developer/debug/zxdb/client/substatement.h"
#include "src/developer/debug/zxdb/client/target.h"
#include "src/developer/debug/zxdb/client/thread.h"
#include "src/developer/debug/zxdb/console/command.h"
#include "src/developer/debug/zxdb/console/command_utils.h"
#include "src/developer/debug/zxdb/console/console.h"
#include "src/developer/debug/zxdb/console/format_location.h"
#include "src/developer/debug/zxdb/console/output_buffer.h"
#include "src/developer/debug/zxdb/console/verbs.h"
#include "src/developer/debug/zxdb/symbols/process_symbols.h"
#include "src/lib/fxl/strings/string_printf.h"

namespace zxdb {

namespace {

const char kStepsShortHelp[] = "steps / ss: Step into specific call.";
const char kStepsHelp[] =
    R"(steps / ss: Step into specific call.

  Alias: ss

  Finds function calls from the current source line and interactively asks which
  one to step into. Execution will stop at the beginning of the selected
  function.

  The function calls are presented in execution order from the current line
  after the current instruction pointer. If the selected function call is not
  executed due to program logic, execution will stop before the first executed
  instruction immediately following it.

Examples

  [zxdb] ss
    1 Controller::GetLaunchTime()
    2 LaunchRocket()
  Step into specific: 2
)";

// This command is executed in three phases, each separated by an async step.
//
//  1. RunVerbSteps: Request identification of the substatements for the current line.
//
// ---- Async while memory is being fetched from the target.
//
//  2. RunStepsWithSubstatements: Once the call information has been collected, interpret it and
//     start the prompt.
//
// ---- Async while the user enters their selection.
//
//  3. CompleteSteps: Actually do the step given the selected item.

Err CompleteSteps(Thread* thread, TargetPointer ip, const std::vector<AddressRange>& ranges,
                  const std::string& one_based_index_str) {
  // Validate that the thread hasn't changed since we prompted.
  if (thread->GetStack().empty() || ip != thread->GetStack()[0]->GetAddress())
    return Err("Thread continued in the background, giving up on \"steps\" command.");

  if (one_based_index_str == "q")
    return Err();  // Don't do anything for "quit".

  size_t chosen_index = 0;  // One-based!
  if (sscanf(one_based_index_str.c_str(), "%zu", &chosen_index) != 1 || chosen_index == 0 ||
      chosen_index > ranges.size()) {
    // The prompt should have validated the input but we double-check.
    FX_NOTREACHED();
    return Err("Bad selected index.");
  }

  auto controller = std::make_unique<StepIntoSpecificThreadController>(ranges[chosen_index - 1]);
  thread->ContinueWith(std::move(controller), [](const Err& err) {
    if (err.has_error())
      Console::get()->Output(err);
  });
  return Err();
}

Err RunVerbSteps(ConsoleContext* context, const Command& cmd) {
  if (Err err = AssertStoppedThreadCommand(context, cmd, true, "steps"); err.has_error())
    return err;

  Process* process = cmd.target()->GetProcess();
  GetSubstatementCallsForLine(process, cmd.frame()->GetLocation(),
                              [weak_thread = cmd.thread()->GetWeakPtr()](
                                  const Err& err, std::vector<SubstatementCall> calls) {
                                if (!weak_thread)
                                  Console::get()->Output(Err("Thread terminated."));
                                else if (err.has_error())
                                  Console::get()->Output(err);
                                else
                                  RunVerbStepsWithSubstatements(weak_thread.get(), calls);
                              });

  return Err();
}

}  // namespace

VerbRecord GetStepsVerbRecord() {
  return VerbRecord(&RunVerbSteps, {"steps", "ss"}, kStepsShortHelp, kStepsHelp,
                    CommandGroup::kStep, SourceAffinity::kSource);
}

void RunVerbStepsWithSubstatements(Thread* thread, std::vector<SubstatementCall> calls) {
  Console* console = Console::get();
  if (thread->GetStack().empty()) {
    console->Output("Can't step non-suspended thread.");
    return;
  }

  if (calls.empty()) {
    console->Output("No function calls from this line.");
    return;
  }

  TargetPointer ip = thread->GetStack()[0]->GetAddress();

  ProcessSymbols* symbols = thread->GetProcess()->GetSymbols();

  FormatLocationOptions format_opts;
  format_opts.func.params = FormatFunctionNameOptions::kElideParams;
  format_opts.func.name.show_global_qual = false;
  format_opts.func.name.elide_templates = true;
  format_opts.func.name.bold_last = true;
  format_opts.show_file_line = false;

  // Collects step over ranges for each option.
  std::vector<AddressRange> ranges;

  line_input::ModalPromptOptions prompt_opts;
  OutputBuffer message;
  for (size_t i = 0; i < calls.size(); i++) {
    if (calls[i].call_addr < ip)
      continue;  // Skip anything already past.

    ranges.emplace_back(ip, calls[i].call_addr);

    auto locs = symbols->ResolveInputLocation(InputLocation(calls[i].call_dest));
    FX_DCHECK(locs.size() == 1);  // Should always get one result for an address lookup.

    std::string index_str = fxl::StringPrintf("%zu", ranges.size());
    prompt_opts.options.push_back(index_str);  // Tell the prompt this is a valid option.

    message.Append(Syntax::kSpecial, fxl::StringPrintf("%3s ", index_str.c_str()));
    message.Append(FormatLocation(locs[0], format_opts));
    message.Append("\n");
  }

  if (ranges.empty()) {
    message.Append("Already past all calls on this line.\n");
    console->Output(message);
    return;
  }

  // Allow "q" to quit.
  prompt_opts.options.push_back("q");
  message.Append(Syntax::kSpecial, "  q");
  message.Append("uit\n");
  prompt_opts.cancel_option = "q";

  // Single-digit entry doesn't require <Enter>.
  prompt_opts.require_enter = calls.size() >= 10;

  console->ModalGetOption(
      prompt_opts, std::move(message), "> ",
      [weak_thread = thread->GetWeakPtr(), ip, ranges](const std::string& input) {
        if (!weak_thread)
          return;
        if (Err err = CompleteSteps(weak_thread.get(), ip, ranges, input); err.has_error())
          Console::get()->Output(err);
      });
}

}  // namespace zxdb