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passing strings back from C/C++ to FTN95

 
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KennyT



Joined: 02 Aug 2005
Posts: 277

PostPosted: Fri Mar 16, 2018 2:49 pm    Post subject: passing strings back from C/C++ to FTN95 Reply with quote

an old chestnut but i'm driving myself round in circles trying to make this work!

i have a routine written in C under VS2017:

int checkout_(char *feature, char *version, char* option, char *mess)

And i want to set the "mess" string back in FTN.

under VS, i can see that:
+ mess 0x32a20ed0 "Licensed number of users already reached.\nFeature: REP5\nLicense path: @localhost Licensing error:-4,132" char *
what do i have to set in my interface routine in FTN do get this back?

i've tried:

c_external checkout 'checkout_' (string, string, string, outstring) : integer*4
c_external checkout 'checkout_' (string, string, string, string) : integer*4
c_external checkout 'checkout_' (string, string, string, ref) : integer*4

with:
ierr = checkout(feature_t, ver_t, opt_t, mess)

what's thee correct way to do it, pretty please!

K
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KennyT



Joined: 02 Aug 2005
Posts: 277

PostPosted: Fri Mar 16, 2018 3:37 pm    Post subject: Reply with quote

ok, i've worked out a way to do it:

in C:
int checkout_(char *feature, char *version, char* option, char **mess)

in FTN:
stdcall checkout 'checkout_' (string, string, string, ref) : integer*4

iadd = loc(mess)
ierr = checkout(feature_t, ver_t, opt_t, iadd)

then the address IADD points to the string and can be copied byte-by-byte to a character variable, testing for CR or LF along the way.

not very elegant, but it seems to work.

K
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wahorger



Joined: 13 Oct 2014
Posts: 456
Location: Morrison, CO, USA

PostPosted: Fri Mar 16, 2018 5:04 pm    Post subject: Reply with quote

If you look at the Windows API calls, many contain a length parameter to define how long the result can be so as not to over-run buffers.

That is what I use when coding "C" routines that need to return character values to FTN95.
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