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/* SPDX-License-Identifier: LGPL-2.1-or-later */
/*
* Copyright (C) 2021, Ideas on Board Oy
*
* backtrace.h - Call stack backtraces
*/
#include <libcamera/base/backtrace.h>
#if HAVE_BACKTRACE
#include <execinfo.h>
#include <stdlib.h>
#endif
#include <sstream>
#include <libcamera/base/span.h>
/**
* \file backtrace.h
* \brief Generate call stack backtraces
*/
namespace libcamera {
/**
* \class Backtrace
* \brief Representation of a call stack backtrace
*
* The Backtrace class represents a function call stack. Constructing an
* instance captures the call stack at the point the instance is constructed.
* The instance can later be used to access the call stack and to generate a
* human-readable representation with the toString() function.
*
* Depending on the platform, different backends can be used to generate the
* backtrace. The Backtrace class provides a best effort to capture accurate
* backtraces, but doesn't offer any guarantee of a particular backtrace format.
*/
/**
* \brief Construct a backtrace
*
* The backtrace captures the call stack at the point where it is constructed.
* It can later be converted to a string with toString().
*/
Backtrace::Backtrace()
{
#if HAVE_BACKTRACE
backtrace_.resize(32);
int num_entries = backtrace(backtrace_.data(), backtrace_.size());
if (num_entries < 0) {
backtrace_.clear();
return;
}
backtrace_.resize(num_entries);
#endif
}
/**
* \brief Convert a backtrace to a string representation
* \param[in] skipLevels Number of initial levels to skip in the backtrace
*
* The string representation of the backtrace is a multi-line string, with one
* line per call stack entry. The format of the entries isn't specified and is
* platform-dependent.
*
* The \a skipLevels parameter indicates how many initial entries to skip from
* the backtrace. This can be used to hide functions that wrap the construction
* of the Backtrace instance from the call stack. The Backtrace constructor
* itself is automatically skipped and never shown in the backtrace.
*
* If backtrace generation fails for any reason (usually because the platform
* doesn't support this feature), an empty string is returned.
*
* \return A string representation of the backtrace, or an empty string if
* backtrace generation isn't possible
*/
std::string Backtrace::toString(unsigned int skipLevels) const
{
/* Skip the first entry, corresponding to the Backtrace construction. */
skipLevels += 1;
if (backtrace_.size() <= skipLevels)
return std::string();
#if HAVE_BACKTRACE
Span<void *const> trace{ backtrace_ };
trace = trace.subspan(skipLevels);
char **strings = backtrace_symbols(trace.data(), trace.size());
if (strings) {
std::ostringstream msg;
for (unsigned int i = 0; i < trace.size(); ++i)
msg << strings[i] << std::endl;
free(strings);
return msg.str();
}
#endif
return std::string();
}
} /* namespace libcamera */
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