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/**
*
* @file SpanLifetimeRule.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 <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 SpanLifetimeKind
{
OutlivedLocalStorage,
UseAfterReturn,
PointsToFreedMemory,
InvalidatedByReallocation,
InvalidatedByResizeOrClear,
ReturnedDanglingSpan,
GenericDanglingSpan,
};
SpanLifetimeKind classify_issue(const std::string &log)
{
if (icontains(log, "use-after-return"))
{
return SpanLifetimeKind::UseAfterReturn;
}
if (icontains(log, "stack-use-after-scope") ||
icontains(log, "use-after-scope"))
{
return SpanLifetimeKind::OutlivedLocalStorage;
}
if (icontains(log, "heap-use-after-free") ||
icontains(log, "use-after-free"))
{
return SpanLifetimeKind::PointsToFreedMemory;
}
if (icontains(log, "reallocation") ||
icontains(log, "reallocated") ||
icontains(log, "reserve") ||
icontains(log, "push_back") ||
icontains(log, "emplace_back"))
{
return SpanLifetimeKind::InvalidatedByReallocation;
}
if (icontains(log, "resize") ||
icontains(log, "clear") ||
icontains(log, "shrink_to_fit"))
{
return SpanLifetimeKind::InvalidatedByResizeOrClear;
}
if (icontains(log, "return") &&
(icontains(log, "span") || icontains(log, "std::span")))
{
return SpanLifetimeKind::ReturnedDanglingSpan;
}
return SpanLifetimeKind::GenericDanglingSpan;
}
std::string choose_message(const std::string &log)
{
switch (classify_issue(log))
{
case SpanLifetimeKind::OutlivedLocalStorage:
return "std::span outlived local storage";
case SpanLifetimeKind::UseAfterReturn:
return "std::span points to data from a returned function";
case SpanLifetimeKind::PointsToFreedMemory:
return "std::span points to freed memory";
case SpanLifetimeKind::InvalidatedByReallocation:
return "std::span invalidated by container reallocation";
case SpanLifetimeKind::InvalidatedByResizeOrClear:
return "std::span invalidated by container resize or clear";
case SpanLifetimeKind::ReturnedDanglingSpan:
return "function returned a dangling std::span";
case SpanLifetimeKind::GenericDanglingSpan:
default:
return "dangling std::span";
}
}
std::string choose_hint(const std::string &log)
{
switch (classify_issue(log))
{
case SpanLifetimeKind::OutlivedLocalStorage:
return "ensure the local array, buffer, or object referenced by std::span outlives the span";
case SpanLifetimeKind::UseAfterReturn:
return "do not return std::span pointing to local variables or temporary storage";
case SpanLifetimeKind::PointsToFreedMemory:
return "avoid keeping std::span after the owning allocation or container is destroyed";
case SpanLifetimeKind::InvalidatedByReallocation:
return "recreate the std::span after vector reserve, push_back, emplace_back, or any operation that may reallocate";
case SpanLifetimeKind::InvalidatedByResizeOrClear:
return "recreate or discard the std::span after resize, clear, erase, or shrink_to_fit";
case SpanLifetimeKind::ReturnedDanglingSpan:
return "return an owning container instead, or ensure the referenced storage outlives the returned span";
case SpanLifetimeKind::GenericDanglingSpan:
default:
return "ensure the array, vector, string, or buffer referenced by std::span stays alive and stable";
}
}
std::vector<std::string> source_patterns_for_span_lifetime()
{
return {
"std::span",
"span<",
"span ",
"std::as_bytes",
"std::as_writable_bytes",
".data()",
"data()",
".size()",
".resize(",
"resize(",
".reserve(",
"reserve(",
".clear(",
"clear(",
".erase(",
"erase(",
".push_back(",
"push_back(",
".emplace_back(",
"emplace_back(",
".shrink_to_fit(",
"shrink_to_fit(",
"delete",
"delete[]",
"free(",
"return",
};
}
bool looks_like_span_lifetime_log(const std::string &log)
{
const bool hasSpanSignal =
icontains(log, "span") ||
icontains(log, "std::span");
const bool hasLifetimeSignal =
icontains(log, "dangling") ||
icontains(log, "lifetime") ||
icontains(log, "invalid") ||
icontains(log, "stack-use-after-scope") ||
icontains(log, "use-after-scope") ||
icontains(log, "use-after-return") ||
icontains(log, "heap-use-after-free") ||
icontains(log, "use-after-free") ||
icontains(log, "outlived") ||
icontains(log, "reallocation") ||
icontains(log, "reallocated");
return hasSpanSignal && hasLifetimeSignal;
}
} // namespace
class SpanLifetimeRule final : public IRuntimeErrorRule
{
public:
bool match(
const std::string &log,
const std::filesystem::path &sourceFile) const override
{
(void)sourceFile;
return looks_like_span_lifetime_log(log);
}
bool handle(
const std::string &log,
const std::filesystem::path &sourceFile) const override
{
const std::string message = choose_message(log);
RuntimeLocation location =
find_best_runtime_location(log, sourceFile);
if (!location.valid())
{
location =
find_best_runtime_location_or_source_hint(
log,
sourceFile,
source_patterns_for_span_lifetime());
}
std::cerr << RED
<< "runtime error: "
<< message
<< RESET << "\n";
if (location.valid())
{
const auto err = make_runtime_location(
location.file,
location.line,
location.column,
message);
print_runtime_codeframe(err);
}
print_runtime_hints_and_at(
{
choose_hint(log),
"do not ignore the runtime log: span lifetime bugs often require comparing the span creation site and the invalid use site",
},
make_at_text(location, sourceFile));
print_runtime_log_excerpt(log, 22);
return true;
}
};
std::unique_ptr<IRuntimeErrorRule> makeSpanLifetimeRule()
{
return std::make_unique<SpanLifetimeRule>();
}
} // namespace vix::cli::errors::runtime