lix/src/libutil/error.hh

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#pragma once
#include "ref.hh"
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#include "types.hh"
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#include <cstring>
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#include <list>
#include <memory>
#include <map>
#include <optional>
#include "fmt.hh"
/* 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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// 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;
column = pos.column;
file = pos.file;
return *this;
}
template <class P>
ErrPos(const P &p)
{
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*this = p;
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}
};
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struct NixCode {
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ErrPos errPos;
std::optional<string> prevLineOfCode;
std::optional<string> errLineOfCode;
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std::optional<string> nextLineOfCode;
};
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struct Trace {
ErrPos pos;
hintformat hint;
};
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struct ErrorInfo {
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Verbosity level;
string name;
string description;
std::optional<hintformat> hint;
std::optional<NixCode> nixCode;
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std::list<Trace> traces;
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static std::optional<string> programName;
};
std::ostream& operator<<(std::ostream &out, const ErrorInfo &einfo);
/* BaseError should generally not be caught, as it has Interrupted as
a subclass. Catch Error instead. */
class BaseError : public std::exception
{
protected:
string prefix_; // used for location traces etc.
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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:
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 string & prefix() const { return prefix_; }
BaseError & addPrefix(const FormatOrString & fs);
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BaseError & addTrace(ErrPos e, hintformat hint);
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const ErrorInfo & info() { calcWhat(); return err; }
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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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}
MakeError(Error, BaseError);
class SysError : public Error
{
public:
int errNo;
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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};
}