diff options
Diffstat (limited to 'docs/exceptions')
-rw-r--r-- | docs/exceptions | 37 |
1 files changed, 0 insertions, 37 deletions
diff --git a/docs/exceptions b/docs/exceptions index d5ecaeead43..bd22de9f25f 100644 --- a/docs/exceptions +++ b/docs/exceptions @@ -71,40 +71,3 @@ unwinding code. catch handler: catch hanlders are always called from the stack unwinding code. The exception object is passed in a local variable (cfg->exvar). - -gcc support for Exceptions -========================== - -gcc supports exceptions in files compiled with the -fexception option. gcc -generates DWARF exceptions tables in that case, so it is possible to unwind the -stack. The method to read those exception tables is contained in libgcc.a, and -in newer versions of glibc (glibc 2.2.5 for example), and it is called -__frame_state_for(). Another usable glibc function is backtrace_symbols() which -returns the function name corresponding to a code address. - -We dynamically check if those features are available using g_module_symbol(), -and we use them only when available. If not available we use the LMF as -fallback. - -Using gcc exception information prevents us from saving the LMF at each native -call, so this is a way to speed up native calls. This is especially valuable -for internal calls, because we can make sure that all internal calls are -compiled with -fexceptions (we compile the whole mono runtime with that -option). - -All native function are able to call function without exception tables, and so -we are unable to restore all caller saved registers if an exception is raised -in such function. Well, its possible if the previous function already saves all -registers. So we only omit the the LMF if a function has an exception table -able to restore all caller saved registers. - -One problem is that gcc almost never saves all caller saved registers, because -it is just unnecessary in normal situations. But there is a trick forcing gcc -to save all register, we just need to call __builtin_unwind_init() at the -beginning of a function. That way gcc generates code to save all caller saved -register on the stack. - - - - -
\ No newline at end of file |