Re: GC_SAFE_SYSTEM_CALL

[Vladimir T. <vtz...@gm...>]

On Oct 29, 2008, at 4:31 PM, Sam Steingold wrote:
> Vladimir Tzankov wrote:
>> On Oct 29, 2008, at 12:59 AM, Gabriel Dos Reis wrote:
>>> On Tue, Oct 28, 2008 at 4:53 PM, Sam Steingold <sd...@gn...> wrote:
>>>> 1. is this c89 syntax?
>>>>
>>>> #define GC_SAFE_SYSTEM_CALL(type,statement)     \
>>>>   ({var type ret;                               \
>>>>     begin_blocking_system_call();               \
>>>>     ret=statement;                              \
>>>>     end_blocking_system_call();                 \
>>>>     ret;})
>>>>
>>>> do non-gcc compilers support it?
>>> it is a GNU extension not supported by all C compilers.
>>> (Intel compiler does support it though).  I wouldn't
>>> recommend it for portable C code.
>>>
>>> "static inline" tends to produce same effect these days.
>>> If the C macro semantics is needed, then I would say, just
>>> go for the C macro!
>> It looks like this is quite popular extension.
>> Intel: ftp://download.intel.com/support/performancetools/c/linux/ 
>> sb/ linuxcompilerscompatibility703.pdf
>> Sun: http://developers.sun.com/sunstudio/downloads/ssx/compilers/  
>> readme.html
>> IBM: http://publib.boulder.ibm.com/infocenter/lnxpcomp/v7v91/  
>> index.jsp?topic=/com.ibm.vacpp7l.doc/getstart/overview/port_gcc.htm
>> however it is non-standard.
>
> MSVC is conspicuously absent.
>
> Bruno, what do you think?
> should we use it?

GC_SAFE_SYSTEM_CALL() (and other new macros introduced for MT) are  
easily fixable.
I missed the Symbol_value() which in MT is defined as:

   #define Symbol_value(obj) \
     *({var Symbol s=TheSymbol(obj);  \
        var clisp_thread_t *thr=current_thread();\
        var gcv_object_t *r;	    \
        r=(s->tls_index && !eq(SYMVALUE_EMPTY,thr->_ptr_symvalues[s- 
 >tls_index]) ? \
	  thr->_ptr_symvalues+s->tls_index : &s->symvalue); \
        r;})

Throughout the code it is used both as L-value and R-value. In order  
to be standard conformant we should have SetSymbolValue() /  
GetSymbolValue() and replace all Symbol_value() occurrences.

Vladimir