C++Talk.NET C++ language newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  JPEG/setjmp always fails          C++Talk.NET Forum Index -> C++ Language (Moderated) View previous topic :: View next topic   Author Message St?phane Vaxelaire Guest Posted: Sat Sep 27, 2003 2:46 pm    Post subject: JPEG/setjmp always fails Hi, I'm working on a project where we had a function that loads a jpeg file. I moved that function into a class that handles images without modifications but now setjmp never returns 0 anymore under win32. The code still works under Linux and MacOS X though. Any idea why setjmp would always return something !=0 only under win32 ?? Any help is greatly appreciated, thanks. Here is the beginning code (full file at http://ewave.homelinux.org/vegastrike/vsimage.cpp) : my_error_mgr jerr; JSAMPARRAY row_pointers=NULL;// Output row buffer cinfo.err = jpeg_std_error(&jerr.pub); jerr.pub.error_exit = my_error_exit; int val; if ((val=setjmp(jerr.setjmp_buffer))) { ....... [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top Jack Klein Guest Posted: Sun Sep 28, 2003 10:25 am    Post subject: Re: JPEG/setjmp always fails On 27 Sep 2003 10:46:34 -0400, [email]surfdargent (AT) free (DOT) fr[/email] (St?phane Vaxelaire) wrote in comp.lang.c++.moderated: Quote: Hi, I'm working on a project where we had a function that loads a jpeg file. I moved that function into a class that handles images without modifications but now setjmp never returns 0 anymore under win32. The code still works under Linux and MacOS X though. Any idea why setjmp would always return something !=0 only under win32 ?? Any help is greatly appreciated, thanks. Here is the beginning code (full file at http://ewave.homelinux.org/vegastrike/vsimage.cpp) : my_error_mgr jerr; JSAMPARRAY row_pointers=NULL;// Output row buffer cinfo.err = jpeg_std_error(&jerr.pub); jerr.pub.error_exit = my_error_exit; int val; if ((val=setjmp(jerr.setjmp_buffer))) { You are calling setjmp in a manner not guaranteed to have defined behavior. Note that the C++ standard does not specifically define the operation of setjmp(), but refers to the C standard, which states: ======== An invocation of the setjmp macro shall appear only in one of the following contexts: — the entire controlling expression of a selection or iteration statement; — one operand of a relational or equality operator with the other operand an integer constant expression, with the resulting expression being the entire controlling expression of a selection or iteration statement; — the operand of a unary ! operator with the resulting expression being the entire controlling expression of a selection or iteration statement; or — the entire expression of an expression statement (possibly cast to void). 5 If the invocation appears in any other context, the behavior is undefined. ======== Now this may not be your problem, but assigning the value returned by setjmp() results in undefined behavior under the language standard. If you must save the actual value returned without invoking undefined behavior, you need to use a switch statement: switch (setjmp(jerr.setjmp_buffer)) { case 0: val = 0; break; case SOME_VALUE: val = SOME_VALUE; break; // etc. } If you eliminate the assignment one way or another and your program still has the error, you have a valid complaint, assuming you have all current service packs installed. If the program works with the assignment eliminated, the compiler is within its rights, no matter how inconvenient it may seem to you. -- Jack Klein Home: http://JK-Technology.Com FAQs for comp.lang.c http://www.eskimo.com/~scs/C-faq/top.html comp.lang.c++ http://www.parashift.com/c++-faq-lite/ alt.comp.lang.learn.c-c++ ftp://snurse-l.org/pub/acllc-c++/faq [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top Display posts from previous: All Posts1 Day7 Days2 Weeks1 Month3 Months6 Months1 Year Oldest FirstNewest First         C++Talk.NET Forum Index -> C++ Language (Moderated) All times are GMT Page 1 of 1   Jump to: Select a forum C/C++----------------C LanguageC Language (Moderated)C++ Language (Moderated)C++ language (comp.lang.c++)C++ language, library and standards Non-English C/C++ Newsgroups----------------C++ (German)C++ (French)  You cannot post new topics in this forum You cannot reply to topics in this forum You cannot edit your posts in this forum You cannot delete your posts in this forum You cannot vote in polls in this forum Powered by phpBB © 2001, 2006 phpBB Group SEO toolkit © 2004-2006 webmedic.