Re: how to build c++

[Andrew Johnson <anj@aps.anl.gov>]

On Tuesday 29 March 2011 07:11:57 yangyong203 wrote:
> My error messages as follow:
> -------------------------------------------------------------------
> /usr/bin/g++ -c  -D_POSIX_C_SOURCE=199506L -D_POSIX_THREADS
> -D_XOPEN_SOURCE=500           -D_X86_  -DUNIX  -D_BSD_SOURCE -Dlinux 
> -D_REENTRANT   -O3   -Wall      -m32     -g -fPIC -I. -I../O.Common -I.
> -I.. -I../../../include/os/Linux -I../../../include
> -I/epics0320/base/include/os/Linux -I/epics0320/base/include       
> ../dbSubExample.cpp
> In file included from ../dbSubExample.cpp:6:
> /epics0320/base/include/aSubRecord.h:163: error: expected unqualified-id
> before ‘!’ token
> ---------------------------------------------------------

Ah, this is a very specific problem with the aSub record, which contains a 
field named 'NOT', which becomes a structure data member 'not'.  The word 
'not' is a reserved word in C++ (which the compiler has replaced with the 
synonym '!' in the above error message) but not in C, thus the dbSubExample.c 
file compiles but it doesn't if you rename it and try to use the C++ compiler.

There is a very simple fix though: Insert the following macro definition into 
your dbSubExample.cpp file before the #include <aSubRecord.h> line:
	#define not no_t
This will change the name that the C++ compiler sees for that data member into 
something that it accepts, and the result should then compile properly.

- Andrew
-- 
An error is only a mistake if you don't learn from it.
When you learn something from it, it becomes a lesson.