[Gm2] Re: How do I declare a character pointer returned from a "C" function?

[Gaius Mulley]

john o goyo <address@hidden> writes:

> Results below.
>
> On 31-Aug-10, at 1:20 PM, Gaius Mulley wrote:
>>> Okay -- my question was too generic.  Specifically, it seems that the
>>> TermFile tests fail on Solaris 10 because TermFile.mod tries to
>>> open /
>>> dev/tty and this does not work in Solaris 10.  The recommended method
>>> is to retrieve the name of the current terminal via ttyname() or
>>> ttyname_r(), preferably the latter.  In both cases, pointers to the
>>> string containing the name are returned.
>>>
>>> I wish to replace the Assign('/dev/tty', a) statement in
>>> TermFile.getname() with a call to ttyname_r() but I do not know how
>>> to define the latter in libc.def.  If I define it as you suggest,
>>> then it is unclear to me how to copy the contents of the string into
>>> a (locus citato).
>>
>>
>> Hi John,
>>
>> I hope you don't mind me CC:ing the list as this technique maybe
>> useful to others interfacing to C based libraries.
>>
>> I understand the question better now I think and would use
>> the module DynamicStrings to create a String and CopyOut the
>> result.  So
>>
>>
>> PROCEDURE getname (d: DeviceTablePtr;
>>                    VAR a: ARRAY OF CHAR) ;
>> BEGIN
>>    Assign('/dev/tty', a)
>> END getname ;
>>
>> could be replaced with the following code:
>>
>> IMPORT DynamicStrings ;
>>
>>   ...
>>
>> PROCEDURE getname (d: DeviceTablePtr;
>>                    VAR a: ARRAY OF CHAR) ;
>> VAR
>>    s: DynamicStrings.String ;
>> BEGIN
>>    s := DynamicStrings.InitStringCharStar(ttyname_r()) ;
>>    DynamicStrings.CopyOut(a, s) ;
>>    s := DynamicStrings.KillString(s)
>> END getname ;
>
> To start, here is the definition of ttyname() from "man ttyname".
>
>       char *ttyname(int fildes);
>
> I defined this as follows in libc.def.
>
>       PROCEDURE ttyname(fildes :INTEGER) :ADDRESS;
>
> Here is the new getname().
>
> PROCEDURE getname (d: DeviceTablePtr;
>                    VAR a: ARRAY OF CHAR) ;
> VAR
>    s: DynamicStrings.String ;
> BEGIN
>    s := DynamicStrings.InitStringCharStar(libc.ttyname(0)) ;
>    DynamicStrings.CopyOut(a, s) ;
>    s := DynamicStrings.KillString(s)
>    (*Assign('/dev/tty', a)*)
> END getname ;
>
> I then rebuilt from scratch and was rewarded with the following.
>
> ./xgm2 -fsoft-check-all -g  -funbounded-by-reference -fiso -fextended- 
> opaque -Wpedantic-cast -Wpedantic-param-names -ffunction-sections - 
> fdata-sections -c -B./stage1/gm2  -g -gdwarf-2 -B./ -Igm2/gm2-libs- 
> iso:../../../src/gcc-4.1.2/gcc/gm2/gm2-libs-iso -I../../../src/
> gcc-4.1.2/gcc/gm2/gm2-libs ../../../src/gcc-4.1.2/gcc/gm2/gm2-libs- 
> iso/TermFile.mod -o gm2/gm2-libs-iso/TermFile.o
> Internal error: Segmentation Fault
>
> Suggestions are welcome.
>

Hi John,

I've just tried the changes and they compile fine on my LP64 x86
system

regards,
Gaius