Re: seq-2.1.12 and C++

[Hovanes Egiyan <hovanes.egiyan@gmail.com>]

Thanks, that's fine for us as well. We have a fix that works for us now,
and then we won't need it when we go to seq-2.2.
Hovanes.


On 08/31/2015 06:01 AM, Benjamin Franksen wrote:
> On Monday 24 August 2015 14:26:12 Hovanes Egiyan wrote:
> > Hi,
> >
> > I was trying to call SNLs C-functions equivalents for pvPut, pvGet,
> > pvAssign etc (seq_pvPut ...)
> > from a C++ code using seq-2.1.12, and run into a compile-time problem.
> > I was getting error messages from g++:
> >
> > /gluex/controls/epics/R3-14-12-3-RHEL5/support/seq-2.1.12/include/seqC
> > om.h:102: error: conflicting declaration ‘typedef const struct seqChan
> > seqChan’
> > /gluex/controls/epics/R3-14-12-3-RHEL5/support/seq-2.1.12/include/seq
> > Com.h:102: error: ‘struct seqChan’ has a previous declaration as
> > ‘struct seqChan’
> > /gluex/controls/epics/R3-14-12-3-RHEL5/support/seq-2.1.12/include/seq
> > Com.h:103: error: conflicting declaration ‘typedef const struct
> > seqState seqState’
> > /gluex/controls/epics/R3-14-12-3-RHEL5/support/seq-2.1.12/include/seq
> > Com.h:103: error: ‘struct seqState’ has a previous declaration as
> > ‘struct seqState’
> > /gluex/controls/epics/R3-14-12-3-RHEL5/support/seq-2.1.12/include/seq
> > Com.h:104: error: conflicting declaration ‘typedef const struct seqSS
> > seqSS’
> > /gluex/controls/epics/R3-14-12-3-RHEL5/support/seq-2.1.12/include/seq
> > Com.h:104: error: ‘struct seqSS’ has a previous declaration as ‘struct
> > seqSS’
> >
> > The problem seems to be coming from seq-2.1.12/src/seq/seqCom.h header
> > file where there are typedef
> > statements for struct structure before actual definition of the
> > structures. C++ does not
> > seem to like it, and I was able to move forward using one "#ifndef
> > __cplusplus" instruction :
> >
> > #ifndef __cplusplus
> > typedef const struct seqChan seqChan;
> > typedef const struct seqState seqState;
> > typedef const struct seqSS seqSS;
> > typedef struct seqProgram seqProgram;
> > #endif
> >
> > /* Static information about a channel */
> > struct seqChan
> > {
> > ...
> >
> > That way these typedefs are not be present for a C++ compiler.
> > I do not know if it breaks anything in the bigger picture,
> Well, the typedefs in question have a 'const' in them, so there is a
> semantic difference. The better solution would be to rename either the
> typedefs or the struct names.
>
> > but if it
> > does not, may be it could
> > be included in the "src/seq/seqCom.h" for the seq module.
> I am reluctant to make this change on the 2.1 branch because there is no
> longer any development happening there except critical bug fixes. The
> problem should not appear with version 2.2, where I have separated the
> definitions that are (meant to be) used only by the generated C code
> (including the 'typedef const struct xxx' definitions that are causing
> your problem) into a separate header file.
>
> So, unless there is strong demand for it, I'd rather point you to
> version 2.2 if you need to call pv functions from C++.
>
> Cheers
> Ben
>
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