lix/src/libutil/error.hh

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#pragma once
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#include "ref.hh"
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#include "types.hh"
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#include "fmt.hh"
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#include <cstring>
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#include <list>
#include <memory>
#include <map>
#include <optional>
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#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
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/* Before 4.7, gcc's std::exception uses empty throw() specifiers for
* its (virtual) destructor and what() in c++11 mode, in violation of spec
*/
#ifdef __GNUC__
#if __GNUC__ < 4 || (__GNUC__ == 4 && __GNUC_MINOR__ < 7)
#define EXCEPTION_NEEDS_THROW_SPEC
#endif
#endif
namespace nix {
/*
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This file defines two main structs/classes used in nix error handling.
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ErrorInfo provides a standard payload of error information, with conversion to string
happening in the logger rather than at the call site.
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BaseError is the ancestor of nix specific exceptions (and Interrupted), and contains
an ErrorInfo.
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ErrorInfo structs are sent to the logger as part of an exception, or directly with the
logError or logWarning macros.
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See the error-demo.cc program for usage examples.
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*/
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typedef enum {
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lvlError = 0,
lvlWarn,
lvlInfo,
lvlTalkative,
lvlChatty,
lvlDebug,
lvlVomit
} Verbosity;
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typedef enum {
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foFile,
foStdin,
foString
} FileOrigin;
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// the lines of code surrounding an error.
struct LinesOfCode {
std::optional<string> prevLineOfCode;
std::optional<string> errLineOfCode;
std::optional<string> nextLineOfCode;
};
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// ErrPos indicates the location of an error in a nix file.
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struct ErrPos {
int line = 0;
int column = 0;
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string file;
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FileOrigin origin;
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operator bool() const
{
return line != 0;
}
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// convert from the Pos struct, found in libexpr.
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template <class P>
ErrPos& operator=(const P &pos)
{
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origin = pos.origin;
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line = pos.line;
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column = pos.column;
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// is file symbol null?
if (pos.file.set())
file = pos.file;
else
file = "";
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return *this;
}
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template <class P>
ErrPos(const P &p)
{
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*this = p;
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}
};
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struct Trace {
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std::optional<ErrPos> pos;
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hintformat hint;
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};
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struct ErrorInfo {
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Verbosity level;
string name;
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string description; // FIXME: remove? it seems to be barely used
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std::optional<hintformat> hint;
std::optional<ErrPos> errPos;
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std::list<Trace> traces;
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static std::optional<string> programName;
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};
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std::ostream& showErrorInfo(std::ostream &out, const ErrorInfo &einfo, bool showTrace);
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/* BaseError should generally not be caught, as it has Interrupted as
a subclass. Catch Error instead. */
class BaseError : public std::exception
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{
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protected:
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mutable ErrorInfo err;
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mutable std::optional<string> what_;
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const string& calcWhat() const;
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public:
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unsigned int status = 1; // exit status
template<typename... Args>
BaseError(unsigned int status, const Args & ... args)
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: err {.level = lvlError,
.hint = hintfmt(args...)
}
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, status(status)
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{ }
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template<typename... Args>
BaseError(const std::string & fs, const Args & ... args)
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: err {.level = lvlError,
.hint = hintfmt(fs, args...)
}
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{ }
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BaseError(hintformat hint)
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: err {.level = lvlError,
.hint = hint
}
{ }
BaseError(ErrorInfo && e)
: err(std::move(e))
{ }
BaseError(const ErrorInfo & e)
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: err(e)
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{ }
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virtual const char* sname() const { return "BaseError"; }
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#ifdef EXCEPTION_NEEDS_THROW_SPEC
~BaseError() throw () { };
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const char * what() const throw () { return calcWhat().c_str(); }
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#else
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const char * what() const noexcept override { return calcWhat().c_str(); }
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#endif
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const string & msg() const { return calcWhat(); }
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const ErrorInfo & info() const { calcWhat(); return err; }
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template<typename... Args>
BaseError & addTrace(std::optional<ErrPos> e, const string &fs, const Args & ... args)
{
return addTrace(e, hintfmt(fs, args...));
}
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BaseError & addTrace(std::optional<ErrPos> e, hintformat hint);
bool hasTrace() const { return !err.traces.empty(); }
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};
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#define MakeError(newClass, superClass) \
class newClass : public superClass \
{ \
public: \
using superClass::superClass; \
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virtual const char* sname() const override { return #newClass; } \
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}
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MakeError(Error, BaseError);
MakeError(UsageError, Error);
MakeError(UnimplementedError, Error);
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class SysError : public Error
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{
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public:
int errNo;
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template<typename... Args>
SysError(const Args & ... args)
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: Error("")
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{
errNo = errno;
auto hf = hintfmt(args...);
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err.hint = hintfmt("%1%: %2%", normaltxt(hf.str()), strerror(errNo));
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}
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virtual const char* sname() const override { return "SysError"; }
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};
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}