为何设置x64架构后链接器仍在x86目录查找LIBCMT.lib？

Windows 10

我找到一款用于S7协议通信的libnodave库，正尝试通过修改后的Makefile编译x64架构的示例程序。

尽管已设置x64库目录（VER=64），但链接器仍在x86目录中查找LIBCMT.lib，这是为什么？将VER=86设置为x86时一切正常。

链接日志关键部分：

C:\Program Files\Microsoft Visual Studio\2022\Community\VC\Tools\MSVC\14.30.30705\lib\x86\LIBCMT.lib : warning LNK4272: library machine type 'x86' conflicts with target machine type 'x64'

Makefile内容： #

#
# Makefile to build a Windows Version of LIBNODAVE using MSVC++ from Microsoft.
#
# The directory where the tools are:
VCPATH=C:\Program Files\Microsoft Visual Studio\2022\Community\VC\Tools\MSVC\14.30.30705
SDKPATH=C:\Program Files (x86)\Windows Kits\10

VER=64

CC="$(VCPATH)\bin\Hostx$(VER)\x$(VER)\cl"
LL="$(VCPATH)\bin\Hostx$(VER)\x$(VER)\link"

CFLAGS= -I"$(VCPATH)\include" -I"$(SDKPATH)\Include\10.0.20348.0\um" -I"$(SDKPATH)\Include\10.0.20348.0\shared" -I"$(SDKPATH)\Include\10.0.20348.0\ucrt" -c -DBCCWIN -DDAVE_LITTLE_ENDIAN -TC
LLFLAGS= /LIBPATH:"$(VCPATH)\lib\x$(VER)" /LIBPATH:"$(SDKPATH)\Lib\10.0.20348.0\ucrt\x$(VER)" /LIBPATH:"$(SDKPATH)\Lib\10.0.20348.0\um\x$(VER)" /DEF:libnodave.DEF 


PROGRAMS=testISO_TCP.exe testISO_TCPload.exe 

LIBRARIES=libnodave.dll

all: $(LIBRARIES) $(PROGRAMS)



libnodave.dll: nodave.obj setportw.obj openSocketw.obj openS7online.obj 
    $(LL) $(LLFLAGS) /DLL nodave.obj setportw.obj openSocketw.obj openS7online.obj "$(SDKPATH)\Lib\10.0.20348.0\um\x$(VER)\WS2_32.Lib" /OUT:libnodave.dll    
testISO_TCP.exe: nodave.obj openSocketw.obj testISO_TCP.obj
    $(LL) $(LFLAGS) testISO_TCP.obj openSocketw.obj nodave.obj "$(SDKPATH)\Lib\10.0.20348.0\um\x$(VER)\WS2_32.Lib" /OUT:$@
testISO_TCPload.exe: nodave.obj  openSocketw.obj testISO_TCPload.obj 
    $(LL) $(LFLAGS) testISO_TCPload.obj openSocketw.obj nodave.obj "$(SDKPATH)\Lib\10.0.20348.0\um\x$(VER)\WS2_32.Lib" /out:testISO_TCPload.exe

#
# delete all but the sources:
#
clean:  
    del /f /q *.tds *.il? *.obj *.map *.lib *.dll *.exe *.exp
distclean:  
    del /f /q *.tds *.il? *.obj *.map

nodave.obj: nodave.c nodave.h
    $(CC) $(CFLAGS) -DDOEXPORT nodave.c
setportw.obj: setportw.c
    $(CC) $(CFLAGS) -DDOEXPORT setportw.c
openSocketw.obj: openSocketw.c
    $(CC) $(CFLAGS) -DDOEXPORT openSocketw.c
openS7online.obj: openS7online.c openS7online.h 
    $(CC) $(CFLAGS) -DDOEXPORT openS7online.c
s7fake.obj: s7fake.c
    $(CC) $(CFLAGS) -DDOEXPORT s7fake.c

核心问题：变量名拼写错误 #

编译testISO_TCP.exe和testISO_TCPload.exe时，链接命令里误用了未定义的LFLAGS变量，而非正确的LLFLAGS。由于LFLAGS未定义，链接器无法读取你配置的x64库路径，只能默认去x86目录查找库文件，最终引发架构冲突警告。

修复步骤 #

直接修改Makefile中两个示例程序的链接规则：

1. 将testISO_TCP.exe规则里的$(LFLAGS)替换为$(LLFLAGS)
2. 将testISO_TCPload.exe规则里的$(LFLAGS)替换为$(LLFLAGS)

修改后的规则如下：

testISO_TCP.exe: nodave.obj openSocketw.obj testISO_TCP.obj
    $(LL) $(LLFLAGS) testISO_TCP.obj openSocketw.obj nodave.obj "$(SDKPATH)\Lib\10.0.20348.0\um\x$(VER)\WS2_32.Lib" /OUT:$@
testISO_TCPload.exe: nodave.obj  openSocketw.obj testISO_TCPload.obj 
    $(LL) $(LLFLAGS) testISO_TCPload.obj openSocketw.obj nodave.obj "$(SDKPATH)\Lib\10.0.20348.0\um\x$(VER)\WS2_32.Lib" /out:testISO_TCPload.exe

额外建议 #

• 编译前执行make clean清理旧的x86目标文件，避免残留的32位obj干扰64位编译
• 可在LLFLAGS中添加/MACHINE:X64，显式指定目标架构，进一步确保编译正确性：

  LLFLAGS= /LIBPATH:"$(VCPATH)\lib\x$(VER)" /LIBPATH:"$(SDKPATH)\Lib\10.0.20348.0\ucrt\x$(VER)" /LIBPATH:"$(SDKPATH)\Lib\10.0.20348.0\um\x$(VER)" /DEF:libnodave.DEF /MACHINE:X64
  

内容的提问来源于stack exchange，提问作者PiotrBzdrega