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我正在开发一个使用 makefile 来制作目标的项目。在这里，我很困惑 makefile 如何从 .cpp 文件生成 .o 文件。

像文件 clientthread_level1_unix.o 必须从 clientthread_level1_unix.cpp 文件生成。但是没有指定使用 *.cpp 文件的地方。

EXTRALIBS = -pthread -lz -ldl -lm
OPENGLLIBS =
LDFLAGS_GL =
LDLIBS = ${APPEXTRALIBS} ${top_builddir}/lib/libwx_based-2.6.a ${EXTRALIBS}

# Compiler used
CXX         = c++
CC          = gcc

CANALOBJS =     ../../common/listenthread_unix.o ../../common/clientthread_level1_unix.o ../../common/devicethread_unix.o \
        ../../common/canalshmem_level1_unix.o ../../common/clientlist.o ../../common/controlobject.o \
        ../../common/devicelist.o ../../common/udpreceivethread_unix.o ../../../vscp/common/vscp.o \
        ../../common/clientthread_level2_unix.o ../../common/canalshmem_level2_unix.o \
        ../../common/tcplistenthread.o
CANALHDRS = ../../common/clientlist.h ../../common/controlobject.h ../../common/devicelist.h \
        ../../common/canal.h ../../common/canaldlldef.h \
        ../../common/version.h ../../common/canal_unix_ipc.h ../../common/CanalShMem_level1_unix.h \
        ../../common/CanalShMem_level2_unix.h ../../common/clientthread_level1_unix.h ../../common/clientthread_level2_unix.h
PROJOBJS    = ../../../common/dllist.o ../../../common/configfile.o ../../../common/crc.o
PROJHDRS    = ../../../common/dllist.h ../../../common/configfile.h
OBJS        = canald.o
HDRS        = canald.h


all:        canald

# Build the Linux executable
canald:     $(OBJS) $(HDRS) $(CANALOBJS) $(CANALHDR) $(PROJOBJS) $(PROJHDRS)
        $(CXX) $(OBJS) $(CANALOBJS) $(PROJOBJS) -o canald $(LIBS) $(LDLIBS)

如果我们也使用隐式规则，那么canald目标也不是这样。 http://www.gnu.org/software/make/manual/make.html#make-Deduces http://www.gnu.org/software/make/manual/make.html#Implicit-Rules

请问这条生产线是如何生产运河的？

    $(CXX) $(OBJS) $(CANALOBJS) $(PROJOBJS) -o canald $(LIBS) $(LDLIBS)
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1 回答 1

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线

 $(CXX) $(OBJS) $(CANALOBJS) $(PROJOBJS) -o canald $(LIBS) $(LDLIBS)

将大约（我跳过未定义的变量）翻译成：

 c++  canald.o ../../common/listenthread_unix.o ../../common/clientthread_level1_unix.o ../../common/devicethread_unix.o \
    ../../common/canalshmem_level1_unix.o ../../common/clientlist.o ../../common/controlobject.o \
    ../../common/devicelist.o ../../common/udpreceivethread_unix.o ../../../vscp/common/vscp.o \
    ../../common/clientthread_level2_unix.o ../../common/canalshmem_level2_unix.o \
    ../../common/tcplistenthread.o \
    ../../../common/dllist.o ../../../common/configfile.o ../../../common/crc.o \
    -o canald /lib/libwx_based-2.6.a -pthread -lz -ldl -lm

即，“正常”编译器调用。由于 有明确的规则canald，因此无需搜索隐含的规则。此外，它是 中的目标规则Makefile，因此它是默认目标。

但是，对于对象canald依赖，不存在显式规则，因此使用隐式规则。

如果您想知道存在哪些隐式规则，请make -p在输出中调用并搜索该模式，例如在您的情况下为%.cpp.

于 2013-03-25T08:35:48.297 回答