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/**
*
* @file DataRaceRule.cpp
* @author Gaspard Kirira
*
* Copyright 2025, Gaspard Kirira. All rights reserved.
* https://github.com/vixcpp/vix
* Use of this source code is governed by a MIT license
* that can be found in the License file.
*
* Vix.cpp
*
*/
#include <vix/cli/errors/runtime/IRuntimeErrorRule.hpp>
#include <vix/cli/errors/runtime/RuntimeRuleUtils.hpp>
#include <cctype>
#include <cstdlib>
#include <filesystem>
#include <iostream>
#include <memory>
#include <string>
#include <vector>
#include <vix/cli/Style.hpp>
using namespace vix::cli::style;
namespace vix::cli::errors::runtime
{
namespace
{
enum class DataRaceKind
{
ReadWriteRace,
WriteWriteRace,
MixedAtomicAccess,
InconsistentLocking,
ThreadSanitizerRace,
GenericRace,
};
std::string trim_copy(const std::string &value)
{
std::size_t begin = 0;
while (begin < value.size() &&
std::isspace(
static_cast<unsigned char>(value[begin])) != 0)
{
++begin;
}
std::size_t end = value.size();
while (end > begin &&
std::isspace(
static_cast<unsigned char>(value[end - 1])) != 0)
{
--end;
}
return value.substr(begin, end - begin);
}
std::string lowercase_copy(std::string value)
{
for (char &character : value)
{
character = static_cast<char>(
std::tolower(
static_cast<unsigned char>(character)));
}
return value;
}
bool technical_details_enabled()
{
const char *level = std::getenv("VIX_LOG_LEVEL");
if (level == nullptr || *level == '\0')
return false;
const std::string value =
lowercase_copy(trim_copy(level));
return value == "debug" ||
value == "trace";
}
bool has_current_read(const std::string &log)
{
return icontains(log, "Read of size");
}
bool has_current_write(const std::string &log)
{
return icontains(log, "Write of size");
}
bool has_previous_read(const std::string &log)
{
return icontains(log, "Previous read of size");
}
bool has_previous_write(const std::string &log)
{
return icontains(log, "Previous write of size");
}
bool has_atomic_access(const std::string &log)
{
/*
* Do not classify a report as atomic merely because an
* unrelated stack frame contains std::atomic.
*
* These phrases describe an actual atomic access in a
* ThreadSanitizer report.
*/
return icontains(log, "Atomic read of size") ||
icontains(log, "Atomic write of size") ||
icontains(log, "Previous atomic read of size") ||
icontains(log, "Previous atomic write of size");
}
bool has_lock_context(const std::string &log)
{
return icontains(log, "Mutexes:") ||
icontains(log, "pthread_mutex_lock") ||
icontains(log, "pthread_mutex_unlock") ||
icontains(log, "std::mutex::lock") ||
icontains(log, "std::mutex::unlock");
}
DataRaceKind classify_data_race(
const std::string &log)
{
if (has_atomic_access(log))
return DataRaceKind::MixedAtomicAccess;
const bool currentRead =
has_current_read(log);
const bool currentWrite =
has_current_write(log);
const bool previousRead =
has_previous_read(log);
const bool previousWrite =
has_previous_write(log);
if (currentWrite && previousWrite)
return DataRaceKind::WriteWriteRace;
if ((currentRead && previousWrite) ||
(currentWrite && previousRead) ||
(currentRead && currentWrite))
{
return DataRaceKind::ReadWriteRace;
}
if (has_lock_context(log))
return DataRaceKind::InconsistentLocking;
if (icontains(log, "ThreadSanitizer"))
return DataRaceKind::ThreadSanitizerRace;
return DataRaceKind::GenericRace;
}
std::string choose_message(
const std::string &log)
{
switch (classify_data_race(log))
{
case DataRaceKind::ReadWriteRace:
return "data race between a read and a write";
case DataRaceKind::WriteWriteRace:
return "data race between concurrent writes";
case DataRaceKind::MixedAtomicAccess:
return "mixed atomic and non-atomic access";
case DataRaceKind::InconsistentLocking:
return "shared state is not consistently locked";
case DataRaceKind::ThreadSanitizerRace:
case DataRaceKind::GenericRace:
default:
return "data race detected";
}
}
std::string choose_description(
const std::string &log)
{
switch (classify_data_race(log))
{
case DataRaceKind::ReadWriteRace:
return "One thread read shared memory while another thread modified it without proper synchronization.";
case DataRaceKind::WriteWriteRace:
return "Two threads modified the same memory at the same time without proper synchronization.";
case DataRaceKind::MixedAtomicAccess:
return "The same shared state appears to be accessed through incompatible atomic and non-atomic operations.";
case DataRaceKind::InconsistentLocking:
return "Some accesses to the shared state appear to bypass the mutex used by other code paths.";
case DataRaceKind::ThreadSanitizerRace:
case DataRaceKind::GenericRace:
default:
return "Multiple threads accessed the same memory concurrently, and at least one access modified it.";
}
}
std::string choose_hint(
const std::string &log)
{
switch (classify_data_race(log))
{
case DataRaceKind::ReadWriteRace:
return "protect every read and write with the same mutex, or use an atomic type when appropriate";
case DataRaceKind::WriteWriteRace:
return "serialize writes with one mutex or give the shared state a single owner";
case DataRaceKind::MixedAtomicAccess:
return "make every access to this value atomic or protect every access with the same mutex";
case DataRaceKind::InconsistentLocking:
return "ensure every code path locks the same mutex before accessing the shared state";
case DataRaceKind::ThreadSanitizerRace:
case DataRaceKind::GenericRace:
default:
return "protect shared mutable state with std::mutex, std::scoped_lock, or std::atomic";
}
}
bool looks_like_data_race_log(
const std::string &log)
{
const bool hasThreadSanitizer =
icontains(log, "ThreadSanitizer") ||
icontains(log, "WARNING: ThreadSanitizer");
const bool explicitlyReportsRace =
icontains(log, "data race");
/*
* "Read of size" and "Write of size" also appear in other
* sanitizer reports. They are considered data-race evidence
* only when ThreadSanitizer context is present.
*/
const bool hasAccessReport =
has_current_read(log) ||
has_current_write(log) ||
has_previous_read(log) ||
has_previous_write(log) ||
has_atomic_access(log);
return explicitlyReportsRace ||
(hasThreadSanitizer && hasAccessReport);
}
void print_error(
const std::string &message,
const std::string &description)
{
std::cerr << RED
<< "runtime error: "
<< message
<< RESET
<< "\n";
if (!description.empty())
{
std::cerr << " "
<< description
<< "\n";
}
}
void print_hints_and_location(
const std::string &hint,
const RuntimeLocation &location)
{
std::vector<std::string> hints;
if (!hint.empty())
hints.push_back(hint);
hints.push_back(
"run with VIX_LOG_LEVEL=debug to compare both conflicting access traces");
/*
* Do not fall back to "source: main.cpp".
*
* A data race normally has two conflicting locations.
* Without a real ThreadSanitizer frame, searching for
* operators such as "=", "++" or lock declarations would
* produce a misleading codeframe.
*/
const std::string at =
location.valid()
? make_at_text(
location,
std::filesystem::path{})
: std::string{};
std::cerr << "\n";
print_runtime_hints_and_at(
hints,
at);
}
void print_debug_log(
const std::string &log)
{
if (!technical_details_enabled())
return;
/*
* The complete ThreadSanitizer report is important because
* it normally contains both conflicting stack traces.
*/
print_runtime_log_excerpt(
log,
24);
}
} // namespace
class DataRaceRule final
: public IRuntimeErrorRule
{
public:
bool match(
const std::string &log,
const std::filesystem::path &sourceFile) const override
{
(void)sourceFile;
return looks_like_data_race_log(log);
}
bool handle(
const std::string &log,
const std::filesystem::path &sourceFile) const override
{
const std::string message =
choose_message(log);
const std::string description =
choose_description(log);
const std::string hint =
choose_hint(log);
/*
* ThreadSanitizer normally provides the exact frame.
*
* Do not use a source-pattern fallback here: a data race
* cannot be located reliably by scanning for assignments,
* increments, thread declarations, or mutex declarations.
*/
const RuntimeLocation location =
find_best_runtime_location(
log,
sourceFile);
print_error(
message,
description);
if (location.valid())
{
std::cerr << "\n";
const auto error =
make_runtime_location(
location.file,
location.line,
location.column,
message);
print_runtime_codeframe(error);
}
print_hints_and_location(
hint,
location);
print_debug_log(log);
return true;
}
};
std::unique_ptr<IRuntimeErrorRule>
makeDataRaceRule()
{
return std::make_unique<DataRaceRule>();
}
} // namespace vix::cli::errors::runtime