error LNK2019: 无法解析的外部符号 MAIN__，函数 main 中引用了该符号

I am compiling using

Windows 10 - IFC Version 15.0.1.148 Build 20141023

I am getting error creating my DLL.  I can create a EXE just fine.

Makerfile

FL = -auto -Qansi_alias- -pad_source -traceback \
-fltconsistency -fpconstant -nogen-interfaces

$(r)5.dll : lib\$(e)$(NM).lib lib\graphics.lib \
	              lib\$(m)$(NM).lib lib\$(r)$(NM).lib \
                  $(r)\$(r)5.$O lib\$(s)$(NM).lib \
                  tpfh2o$(NM) tpfd2o$(NM)
	$(f90) -nologo $(FFLAGS) $(FPSTOP) $(FL) -threads -dll \
	$(r)\$(r)5.$O lib\$(r)$(NM).lib lib\$(s)$(NM).lib \
	lib\$(m)$(NM).lib lib\$(e)$(NM).lib \
	lib\graphics.lib libmmt.lib kernel32.lib ifqwin.lib gdi32.lib \
	libifcoremt.lib libifport.lib \
	user32.lib libirc.lib comdlg32.lib ifqw_mdi.lib libcmt.lib \
	imagehlp.lib opengl32.lib glu32.lib lib\f90gl.lib lib\f90glu.lib \
	lib\f90glut.lib lib\glut32.lib -link -out:$(r)5.dll -nodefaultlib

The error that I am getting is:

libifcoremt.lib(for_main.obj) : error LNK2019: unresolved external symbol _MAIN__ referenced in function _main
relap5.dll : fatal error LNK1120: 1 unresolved externals

Try placing the -dll option after -link to ensure it is passed to the link phase. It seems like the error indicates the link wants to create an .exe instead of a DLL.

笔者的问题并不是因为以上，文件和函数明明都在问什么无法链接呢。

测试后发现是添加的cpp文件无法编译导致，测试方法就是Ctrl+F7，编译该文件，发现没反应，就需要将源文件移除，重新添加即可