Experimental Physics and
Industrial Control System

Xiaoqiang Wang <[email protected]> · Thu, 20 Feb 2014 09:47:22 +0100

For the archive purpose, I forward this answer from Peter Heesterman.

Begin forwarded message:

> From: "Heesterman, Peter J" <[email protected]>
> Subject: RE: epics base with MinGW-w64
> Date: 18 Feb 2014 15:10:42 GMT+1
> To: "Wang Xiaoqiang" <[email protected]>
> 
> Hi Wang,
> 
> You are correct in saying that the _DLL macro is wrongly used in sharelib.h - it is a conceptual error, meaning as it does that code is being DLL-linked to Microsoft's VS libraries.
> The EPICS_DLL_NO macro is correct to say that code is being built statically to EPICS user libraries.
> 
> It has been corrected, for later releases.
> 
> Cheers,
> 
> Peter.
> 
> 
> -----Original Message-----
> From: [email protected] [mailto:[email protected]] On Behalf Of Wang Xiaoqiang
> Sent: 18 February 2014 12:13
> To: epics
> Subject: epics base with MinGW-w64
> 
> Hi core developers,
> 
> Sorry this is a long post and the question at the very end.
> 
> I am using MinGW- w64 (http://mingw-w64.sourceforge.net/) on a Windows 7 64bit PC to compile base 3.14.12.4.
> It builds all OK by default. It stops with errors if configured to build statically.
> 
> make[1]: Entering directory
> `C:/epics/base-3.14.12.4-VC9/src/toolsComm/antelope/O.windows-x64-mingw'
> ""
> gcc -c             -D_MINGW     -O3   -Wall     -m64   -DEPICS_DLL_NO
> -MMD -I. -I../O.Common -I. -I.. -I../../../../include/os/WIN32
> -I../../../../include    ../main.c
> g++ -o antelope.exe -static
> -LC:/epics/base-3.14.12.4-VC9/lib/windows-x64-mingw     -m64     
>  closure.o error.o lalr.o lr0.o main.o mkpar.o output.o reader.o
> skeleton.o symtab.o verbose.o warshall.o   -lCom      -lws2_32
> main.o:main.c:(.text.startup+0x2a6): undefined reference to `__imp_epicsTempFile'
> collect2.exe: error: ld returned 1 exit status
> make[1]: *** [antelope.exe] Error 1
> make[1]: Leaving directory
> `C:/epics/base-3.14.12.4-VC9/src/toolsComm/antelope/O
> .windows-x64-mingw'
> make: *** [install.windows-x64-mingw] Error 2
> 
> Looking at base-3.14.12.4-VC9/include/shareLib.h, it is apparently somewhere '_DLL' has be defined.
> And indeed it is that MinGW-w64 always has '_DLL' defined in '_mingw.h',
> /* We have to define _DLL for gcc based mingw version. This define is set
>   by VC, when DLL-based runtime is used. So, gcc based runtime just have
>   DLL-base runtime, therefore this define has to be set.
>   As our headers are possibly used by windows compiler having a static
>   C-runtime, we make this definition gnu compiler specific here.  */ #if !defined (_DLL) && defined (__GNUC__) #define _DLL #endif
> 
> So far the fault is on the side of MinGW-w64. 
> 
> But I have a question about the valid use of '_DLL' macro in 'shareLib.h'
> According to MSDN, _DLL is defined when epics is built to DLL libraries, otherwise not.
> It is perfectly fine if both client program and epics base are built statically or dynamically.
> If one wants to mix them, there is the problem. 
> I often need to compile my python extensions (DLLs by its essence) to link to EPICS statically.
> In such cases, _DLL is defined because the "client program" is compiled to DLL not the "EPICS base libraries". 
> This will cause confusion, I workaround it by undefine _DLL macro.
> 
> So now it comes to my question: since macro EPICS_DLL_NO is the only indication whether EPICS base is built statically or not, is it valid to use it instead of _DLL in shareLib.h ......
> #   else
> #       if not defined(EPICS_DLL_NO) /* this indicates that we are being
> compiled to call DLLs */
> #           define epicsShareExtern __declspec(dllimport) extern 
> #           define epicsShareClass  __declspec(dllimport) 
> #           define epicsShareFunc  __declspec(dllimport)
> #       else
> #           define epicsShareExtern extern
> #           define epicsShareClass
> #           define epicsShareFunc
> #       endif
> ......
> 
> Best
> Xiaoqiang
> 

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System