Re: [LAD] C - Change in memory causing seg.fault (but why?)
On Fri, Nov 09, 2012 at 03:24:56PM +0100, Muffinman wrote: Yeah, that explains why I didn't get any compiling error on a 32bit computer and did get on a 64bit one (where I did correct the error). However, the latter was satisfied with %li. Apparently in c++ there is no difference between long and long int (as far as I can find through Google) but for c I could not find much info on a potential difference. long is the same as long int in both. The problem is that int and long int are both 32 bits on i386, but on x86-64 int is 32 and long int is 64 bits. John ___ Linux-audio-dev mailing list Linux-audio-dev@lists.linuxaudio.org http://lists.linuxaudio.org/listinfo/linux-audio-dev
Re: [LAD] C - Change in memory causing seg.fault (but why?)
On 11/10/2012 10:35 AM, John Rigg wrote: On Fri, Nov 09, 2012 at 03:24:56PM +0100, Muffinman wrote: Yeah, that explains why I didn't get any compiling error on a 32bit computer and did get on a 64bit one (where I did correct the error). However, the latter was satisfied with %li. Apparently in c++ there is no difference between long and long int (as far as I can find through Google) but for c I could not find much info on a potential difference. long is the same as long int in both. The problem is that int and long int are both 32 bits on i386, but on x86-64 int is 32 and long int is 64 bits. spot on. It's architecture dependent. Here's an index: http://www.makelinux.net/ldd3/chp-11-sect-1 For printing, one can use inttypes.h printf(val= PRId64 \n, (int64_t) val); The only problematic one is size_t. printf's %z %Z is a GNU libc extension. Back on topic, a good general introduction to pointers, malloc etc is http://cslibrary.stanford.edu/102/PointersAndMemory.pdf ciao, robin ___ Linux-audio-dev mailing list Linux-audio-dev@lists.linuxaudio.org http://lists.linuxaudio.org/listinfo/linux-audio-dev
Re: [LAD] C - Change in memory causing seg.fault (but why?)
On 09-11-12 01:58, Jacob wrote: And, BTW, pay attention to the format ‘%i’ expects type ‘int’ type of warnings. Using the wrong or omitting required length modifiers can lead to segfaults, too. Even if '%d' and '%ld' refer to integers of the same size on an i386 platform, on a 64 bit platform they won't and weird things can happen if the argument doesn't match the format spec. Jacob Yeah, that explains why I didn't get any compiling error on a 32bit computer and did get on a 64bit one (where I did correct the error). However, the latter was satisfied with %li. Apparently in c++ there is no difference between long and long int (as far as I can find through Google) but for c I could not find much info on a potential difference. Perhaps the resource provided by Tristan can help with that (@Tristan: btw, thanks for that). I will go through that in the coming week. Maarten ___ Linux-audio-dev mailing list Linux-audio-dev@lists.linuxaudio.org http://lists.linuxaudio.org/listinfo/linux-audio-dev
Re: [LAD] C - Change in memory causing seg.fault (but why?)
On Fri, Nov 9, 2012 at 9:24 AM, Muffinman n...@koster.tk wrote: Apparently in c++ there is no difference between long and long int (as far as I can find through Google) but for c I could not find much info on a potential difference. they are different in C++ as well. ___ Linux-audio-dev mailing list Linux-audio-dev@lists.linuxaudio.org http://lists.linuxaudio.org/listinfo/linux-audio-dev
Re: [LAD] C - Change in memory causing seg.fault (but why?)
Maarten: On 09-11-12 01:58, Jacob wrote: And, BTW, pay attention to the format %i expects type int type of warnings. Using the wrong or omitting required length modifiers can lead to segfaults, too. Even if '%d' and '%ld' refer to integers of the same size on an i386 platform, on a 64 bit platform they won't and weird things can happen if the argument doesn't match the format spec. Jacob Yeah, that explains why I didn't get any compiling error on a 32bit computer and did get on a 64bit one (where I did correct the error). However, the latter was satisfied with %li. Apparently in c++ there is no difference between long and long int (as far as I can find through Google) but for c I could not find much info on a potential difference. If you look in the c standard or one of its drafts, e.g. this one: http://www.open-std.org/JTC1/SC22/WG14/www/docs/n1256.pdf In (pdf)page 111 (written page 99) you'll find: [qoute] 6.7.2 Type specifiers ... 2 At least one type specifier shall be given in the declaration specifiers in each declaration, and in the specifier-qualifier list in each struct declaration and type name. Each list of type specifiers shall be one of the following sets (delimited by commas, when there is more than one set on a line); the type specifiers may occur in any order, possibly intermixed with the other declaration specifiers. -- void -- char -- signed char -- unsigned char -- short, signed short, short int, or signed short int -- unsigned short, or unsigned short int -- int, signed, or signed int [newpage] -- unsigned, or unsigned int -- long, signed long, long int, or signed long int -- unsigned long, or unsigned long int -- long long, signed long long, long long int, or signed long long int -- unsigned long long, or unsigned long long int -- float -- double -- long double -- _Bool -- float _Complex -- double _Complex -- long double _Complex -- struct or union specifier -- enum specifier -- typedef name ... 5 Each of the comma-separated sets designates the same type, except that for bit-fields, it is implementation-defined whether the specifier int designates the same type as signed int or the same type as unsigned int. [end qoute] I.e. long and long int designates the same type. Regards, /Karl Hammar --- Aspö Data Lilla Aspö 148 S-742 94 Östhammar Sweden +46 173 140 57 ___ Linux-audio-dev mailing list Linux-audio-dev@lists.linuxaudio.org http://lists.linuxaudio.org/listinfo/linux-audio-dev
Re: [LAD] C - Change in memory causing seg.fault (but why?)
On Fri, Nov 9, 2012 at 9:37 AM, Paul Davis p...@linuxaudiosystems.comwrote: On Fri, Nov 9, 2012 at 9:24 AM, Muffinman n...@koster.tk wrote: Apparently in c++ there is no difference between long and long int (as far as I can find through Google) but for c I could not find much info on a potential difference. they are different in C++ as well. i am sorry, i misread this thinking you said long and long long. sincere apologies for the confusion. ___ Linux-audio-dev mailing list Linux-audio-dev@lists.linuxaudio.org http://lists.linuxaudio.org/listinfo/linux-audio-dev
Re: [LAD] C - Change in memory causing seg.fault (but why?)
On Thu, Nov 8, 2012 at 3:42 PM, Muffinman n...@koster.tk wrote: I'm working on a little app utilizing 'lasound' and I've got bassically what I want. However, somewhere there is a fault. Editing a random variable causes a segmentation fault. I've tried gdb but except it telling me where the application crashed (which I already knew) I did not get anything useful out of it. To minimize my own potential errors I have here below the example script from where I started (though I have removed some unnecessary stuff) and commented out the 'long *outvl' and '*outvl = -1'. Uncommenting, compile, and run this and I get a segmentation fault. You never allocate memory for the pointer long *outvl after you create it, but then try to point to a value. You need to use malloc() to initialize the memory for that pointer before you can use it. -- Brett W. McCoy -- http://www.brettwmccoy.com In the rhythm of music a secret is hidden; If I were to divulge it, it would overturn the world. -- Jelaleddin Rumi ___ Linux-audio-dev mailing list Linux-audio-dev@lists.linuxaudio.org http://lists.linuxaudio.org/listinfo/linux-audio-dev
Re: [LAD] C - Change in memory causing seg.fault (but why?)
On 08-11-12 22:02, Brett McCoy wrote: You never allocate memory for the pointer long *outvl after you create it, but then try to point to a value. You need to use malloc() to initialize the memory for that pointer before you can use it. Thanks!! I believe I have some more reading to do. ___ Linux-audio-dev mailing list Linux-audio-dev@lists.linuxaudio.org http://lists.linuxaudio.org/listinfo/linux-audio-dev
Re: [LAD] C - Change in memory causing seg.fault (but why?)
On 11/08/2012 10:18 PM, Muffinman wrote: On 08-11-12 22:02, Brett McCoy wrote: You never allocate memory for the pointer long *outvl after you create it, but then try to point to a value. You need to use malloc() to initialize the memory for that pointer before you can use it. Thanks!! I believe I have some more reading to do. And, BTW, pay attention to the format ‘%i’ expects type ‘int’ type of warnings. Using the wrong or omitting required length modifiers can lead to segfaults, too. Even if '%d' and '%ld' refer to integers of the same size on an i386 platform, on a 64 bit platform they won't and weird things can happen if the argument doesn't match the format spec. Jacob ___ Linux-audio-dev mailing list Linux-audio-dev@lists.linuxaudio.org http://lists.linuxaudio.org/listinfo/linux-audio-dev
