Makefile开头是 @SET_MAKE@
什么意思？

@@两个符号中加加个变量又是什么意思？？

在编译smartmontools-5.38是看到里面有个Makefile.am文件里就是这么写着。。。
请指点

==============================
[code=BatchFile]
@SET_MAKE@

# Make sure .cpp takes precedence to avoid compiling old .c file
SUFFIXES = .cpp .c .s .o


AM_CPPFLAGS = -DSMARTMONTOOLS_SYSCONFDIR="$(sysconfdir)"

sbin_PROGRAMS = smartd 
smartctl

smartd_SOURCES =  smartd.cpp      
                  smartd.h        
                  atacmdnames.cpp 
                  atacmdnames.h   
                  atacmds.cpp     
                  atacmds.h       
                  ataprint.cpp    
                  ataprint.h      
                  extern.h        
                  int64.h         
                  knowndrives.cpp 
                  knowndrives.h   
                  scsicmds.cpp    
                  scsicmds.h      
                  scsiata.cpp     
                  scsiata.h       
                  scsiprint.cpp   
                  scsiprint.h     
                  utility.cpp     
                  utility.h

smartd_LDADD = @os_deps@ @os_libs@
smartd_DEPENDENCIES = @os_deps@

EXTRA_smartd_SOURCES = os_darwin.cpp    
                       os_darwin.h      
                       os_linux.cpp     
                       os_linux.h       
                       os_freebsd.cpp   
                       os_freebsd.h     
                       os_netbsd.cpp    
                       os_netbsd.h      
                       os_openbsd.cpp   
                       os_openbsd.h     
                       os_solaris.cpp   
                       os_solaris.h     
                       os_solaris_ata.s 
                       os_win32.cpp     
                       os_generic.cpp   
                       os_generic.h     
                       cciss.cpp        
                       cciss.h


if OS_WIN32_MINGW

smartd_SOURCES +=                           
                posix/regex.h               
                posix/regex.c               
                os_win32/daemon_win32.h     
                os_win32/daemon_win32.cpp   
                os_win32/hostname_win32.h   
                os_win32/hostname_win32.cpp 
                os_win32/syslog.h           
                os_win32/syslog_win32.cpp

# Included by regex.c:
EXTRA_smartd_SOURCES +=                   
                posix/regcomp.c           
                posix/regexec.c           
                posix/regex_internal.c    
                posix/regex_internal.h

endif

smartctl_SOURCES= smartctl.cpp    
                  smartctl.h      
                  atacmdnames.cpp 
                  atacmdnames.h   
                  atacmds.cpp     
                  atacmds.h       
                  ataprint.cpp    
                  ataprint.h      
                  extern.h        
                  int64.h         
                  knowndrives.cpp 
                  knowndrives.h   
                  scsicmds.cpp    
                  scsicmds.h      
                  scsiata.cpp     
                  scsiata.h       
                  scsiprint.cpp   
                  scsiprint.h     
                  utility.cpp     
                  utility.h

smartctl_LDADD = @os_deps@ @os_libs@
smartctl_DEPENDENCIES = @os_deps@
[/code]

宏： AC_PROG_MAKE_SET 
如果make预定义了变量MAKE，把输出变量SET_MAKE定义为空。否则，把 SET_MAKE定义成`MAKE=make'。为SET_MAKE调用AC_SUBST。 

为了使用这个宏，在每个其他的、运行MAKE的目录中的`Makefile.in'添加一行： 

@SET_MAKE@ 



[url=http://www.cndw.com/tech/server/2006040431621.asp]

http://sources.redhat.com/ml/automake/2000-01/msg00005.html

http://www.cndw.com/tech/server/2006040431621.asp