How to throw an exception in C

Question

I typed this into google but only found howtos in C     how to do it in C

User · Answer

There are no exceptions in C  In C the errors are notified by the returned value of the function  the exit value of the process  signals to the process  Program Error Signals  GNU libc   or the CPU hardware interruption  or other notification error form the CPU if there is  How processor handles the case of division by zero    Exceptions are defined in C   and other languages though  Exception handling in C   is specified in the C   standard  S 15 Exception handling   there is no equivalent section in the C standard

User · Answer

This question is super old  but I just stumbled across it and thought I d share a technique  divide by zero  or dereference a null pointer    The question is simply  how to throw   not how to catch  or even how to throw a specific type of exception  I had a situation ages ago where we needed to trigger an exception from C to be caught in C    Specifically  we had occasional reports of  pure virtual function call  errors  and needed to convince the C runtime s  purecall function to throw something  So we added our own  purecall function that divided by zero  and boom  we got an exception that we could catch on C    and even use some stack fun to see where things went wrong

User · Answer

Plain old C doesn t actually support exceptions natively   You can use alternative error handling strategies  such as    returning an error code returning FALSE and using a last error variable or function    See http   en wikibooks org wiki C Programming Error handling

User · Answer

On Win with MSVC there s   try       except     but it s really horrible and you don t want to use it if you can possibly avoid it  Better to say that there are no exceptions

User · Answer

If you write code with Happy path design pattern  i e  for embedded device  you may simulate exception error processing  aka deffering or finally emulation  with operator  goto    int process int port        int rc      int fd1      int fd2       fd1   open   dev                 if  fd1    -1          rc   -1        goto out             fd2   open   dev                 if  fd2    -1          rc   -1        goto out                Do some with fd1 and fd2 for example write f2  read fd1        rc   0      out         if  rc    0             void close fd1            void close fd2                return rc      It does not actually exception handler but it take you a way to handle error at fucntion exit   P S  You should be careful use goto only from same or more deep scopes and never jump variable declaration

User · Answer

C is able to throw C   exception  they are machine codes anyway  For example  in bar c      begin bar c  include  lt stdlib h gt   include  lt stdint h gt  extern void    cxa allocate exception size t thrown size   extern void   cxa throw  void  thrown exception  void   tinfo  void   dest   void       extern void    ZTIl     typeinfo of long int bar1        int64 t   p    int64 t    cxa allocate exception 8       p   1976       cxa throw p  amp  ZTIl 0     return 10       end bar c   in a cc    include  lt stdint h gt   include  lt cstdio gt  extern  C  int bar1    void foo       try      bar1       catch int64 t x       printf  good  ld  x         int main int argc  char  argv        foo      return 0      to compile it  gcc -o bar o -c bar c  amp  amp  g   a cc bar o  amp  amp    a out   output  good 1976   http   mentorembedded github io cxx-abi abi-eh html has more detail info about   cxa throw   I am not sure whether it is portable or not  and I test it with  gcc-4 8 2  on Linux

User · Answer

In C you could use the combination of the setjmp   and longjmp   functions  defined in setjmp h  Example from Wikipedia   include  lt stdio h gt   include  lt setjmp h gt   static jmp buf buf   void second void        printf  second n               prints     longjmp buf 1                  jumps back to where setjmp                                       was called - making setjmp now return 1    void first void        second        printf  first n                does not print    int main            if     setjmp buf              first                      when executed  setjmp returns 0       else                         when longjmp jumps back  setjmp returns 1         printf  main               prints            return 0      Note  I would actually advise you not to use them as they work awful with C    destructors of local objects wouldn t get called  and it is really hard to understand what is going on  Return some kind of error instead

User · Answer

C doesn t have exceptions   There are various hacky implementations that try to do it  one example at  http   adomas org excc

User · Answer

C doesn t support exceptions  You can try compiling your C code as C   with Visual Studio or G   and see if it ll compile as-is  Most C applications will compile as C   without major changes  and you can then use the try    catch syntax

User · Answer

As mentioned in numerous threads  the  standard  way of doing this is using setjmp longjmp  I posted yet another such solution to https   github com psevon exceptions-and-raii-in-c This is to my knowledge the only solution that relies on automatic cleanup of allocated resources  It implements unique and shared smartpointers  and allows intermediate functions to let exceptions pass through without catching and still have their locally allocated resources cleaned up properly

User · Answer

Implementing exceptions in c by Eric Roberts Chapter 4 of C Interfaces and Implementations by Hanson  A Discipline of Error Handling by Doug Moen Implementing Exceptions in C  details the article of E Roberts

User · Answer

There s no built-in exception mechanism in C  you need to simulate exceptions and their semantics  This is usually achieved by relying on setjmp and longjmp   There are quite a few libraries around  and I m implementing yet another one  It s called exceptions4c  it s portable and free  You may take a look at it  and compare it against other alternatives to see which fits you most

[c] How to throw an exception in C?

Examples related to c

Examples related to exception

Examples related to syntax