Re: [git commit] libubacktrace: use -funwind-tables rather than -fexecptions
On 04/01/2012 23.36, Mike Frysinger wrote: On Tuesday 03 January 2012 11:34:40 Carmelo AMOROSO wrote: On 01/01/2012 0.10, Mike Frysinger wrote: On Thursday 22 December 2011 13:19:22 Carmelo AMOROSO wrote: On 22/12/2011 15.30, Carmelo Amoroso wrote: For backtrace to work is enough to use -funwind-tables instead of -fexceptions. Indeed, I'm wondering if -fasynchrous-unwind-tables should be used rather then funwind-tables. On my arh SH4 the generated code is exactly the same. I'm not expert of DWARF, neither gcc documentation regarding the differences between -fexceptions, -funwind-tables or -fasynchronous-unwind-tables helped me so much. someone else has clearer idea ? for backtrace, we just want unwind-tables, so using that over -fexceptions is good (since we don't have to handle exceptions in this code). as for the async vs non-async unwind-tables, i don't know the answer to that. I've reported here below the extract from gcc manual. Reading it again, it seems to me that using -fasynchronous-unwind-tables is the best as it's purpose is actually to create the dwarf2 information, in the other two cases (-fexceptions or -funwind-tables) it seems to be a side effect. glibc seems to prefer -fasynchronous-unwind-tables, so that's probably good for us too we need -fexceptions if the funcs themselves need to handle exceptions. but if we only want other things to be able to build a backtrace across the call, then -fasynchronous-unwind-tables should be sufficient. -mike agreed. I'll commit an update shortly. carmelo ___ uClibc mailing list uClibc@uclibc.org http://lists.busybox.net/mailman/listinfo/uclibc
Re: [git commit] libubacktrace: use -funwind-tables rather than -fexecptions
On Tuesday 03 January 2012 11:34:40 Carmelo AMOROSO wrote: On 01/01/2012 0.10, Mike Frysinger wrote: On Thursday 22 December 2011 13:19:22 Carmelo AMOROSO wrote: On 22/12/2011 15.30, Carmelo Amoroso wrote: For backtrace to work is enough to use -funwind-tables instead of -fexceptions. Indeed, I'm wondering if -fasynchrous-unwind-tables should be used rather then funwind-tables. On my arh SH4 the generated code is exactly the same. I'm not expert of DWARF, neither gcc documentation regarding the differences between -fexceptions, -funwind-tables or -fasynchronous-unwind-tables helped me so much. someone else has clearer idea ? for backtrace, we just want unwind-tables, so using that over -fexceptions is good (since we don't have to handle exceptions in this code). as for the async vs non-async unwind-tables, i don't know the answer to that. I've reported here below the extract from gcc manual. Reading it again, it seems to me that using -fasynchronous-unwind-tables is the best as it's purpose is actually to create the dwarf2 information, in the other two cases (-fexceptions or -funwind-tables) it seems to be a side effect. glibc seems to prefer -fasynchronous-unwind-tables, so that's probably good for us too we need -fexceptions if the funcs themselves need to handle exceptions. but if we only want other things to be able to build a backtrace across the call, then -fasynchronous-unwind-tables should be sufficient. -mike signature.asc Description: This is a digitally signed message part. ___ uClibc mailing list uClibc@uclibc.org http://lists.busybox.net/mailman/listinfo/uclibc
Re: [git commit] libubacktrace: use -funwind-tables rather than -fexecptions
On 01/01/2012 0.10, Mike Frysinger wrote: On Thursday 22 December 2011 13:19:22 Carmelo AMOROSO wrote: On 22/12/2011 15.30, Carmelo Amoroso wrote: commit: http://git.uclibc.org/uClibc/commit/?id=8a8434b367e0b94b9fda72c99f1c6467 37725403 branch: http://git.uclibc.org/uClibc/commit/?id=refs/heads/master For backtrace to work is enough to use -funwind-tables instead of -fexceptions. Signed-off-by: Carmelo Amoroso carmelo.amor...@st.com Indeed, I'm wondering if -fasynchrous-unwind-tables should be used rather then funwind-tables. On my arh SH4 the generated code is exactly the same. I'm not expert of DWARF, neither gcc documentation regarding the differences between -fexceptions, -funwind-tables or -fasynchronous-unwind-tables helped me so much. someone else has clearer idea ? for backtrace, we just want unwind-tables, so using that over -fexceptions is good (since we don't have to handle exceptions in this code). as for the async vs non-async unwind-tables, i don't know the answer to that. -mike Thanks Mike for your feedback. I've reported here below the extract from gcc manual. Reading it again, it seems to me that using -fasynchronous-unwind-tables is the best as it's purpose is actually to create the dwarf2 information, in the other two cases (-fexceptions or -funwind-tables) it seems to be a side effect. Make sense ? Cheers, Carmelo -fexceptions Enable exception handling. Generates extra code needed to propagate exceptions. For some targets, this implies GCC will generate frame unwind information for all functions, which can produce significant data size overhead, although it does not affect execution. If you do not specify this option, GCC will enable it by default for languages like C++ which normally require exception handling, and disable it for languages like C that do not normally require it. However, you may need to enable this option when compiling C code that needs to interoperate properly with exception handlers written in C++. You may also wish to disable this option if you are compiling older C++ programs that don't use exception handling. -funwind-tables Similar to -fexceptions, except that it will just generate any needed static data, but will not affect the generated code in any other way. You will normally not enable this option; instead, a language processor that needs this handling would enable it on your behalf. -fasynchronous-unwind-tables Generate unwind table in dwarf2 format, if supported by target machine. The table is exact at each instruction boundary, so it can be used for stack unwinding from asynchronous events (such as debugger or garbage collector). ___ uClibc-cvs mailing list uclibc-...@uclibc.org http://lists.busybox.net/mailman/listinfo/uclibc-cvs ___ uClibc mailing list uClibc@uclibc.org http://lists.busybox.net/mailman/listinfo/uclibc
