C++ 在makefile中创建一个库文件然后编译
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Creating a library file in makefile and compiling after that
提问by Mare
My problem is fairly easy but I just don't know how to solve it. I know how to compile and library and link against it if I'm not using a make file because then I can just call ar separately and everything goes right.
我的问题很简单，但我只是不知道如何解决它。如果我不使用 make 文件，我知道如何编译和库并链接它，因为这样我就可以单独调用 ar 并且一切正常。
Anyway I'm using a petsclibrary and I'm using a makefile what they provided:
无论如何，我使用的是petsc库，我使用的是他们提供的 makefile：
CFLAGS =
FFLAGS =
CPPFLAGS =
FPPFLAGS =
LOCDIR = /home/user/.../.../ # Working folder
EXAMPLESC = main.cpp class.cpp #.cpp file names here
EXAMPLESF =
#MANSEC = Mat I don't know what this is but it seems to work without it.
include ${PETSC_DIR}/conf/variables
include ${PETSC_DIR}/conf/rules
myProgram: main.o class.o chkopts
-${CLINKER} -o myProgram main.o class.o ${PETSC_MAT_LIB}
${RM} main.o class.o
include ${PETSC_DIR}/conf/test
ARFLAGS will be -rv as a default so where should I provide such a information as
ARFLAGS 将 -rv 作为默认值，所以我应该在哪里提供这样的信息
ar -rv libclassdll.a class.o
and where should I add -L./-lclassdll ?
我应该在哪里添加 -L./-lclassdll ？
I'm quite a rookie with makefiles so that's why I'm a bit lost here :<
我是一个使用 makefile 的新手，所以这就是我在这里有点迷失的原因：<
I tried to change the line to
我试图将线路更改为
myProgram: main.o class.o chkopts
-${CLINKER} -o myProgram main.o class.o ${AR} libclassdll.a class.o ${PETSC_MAT_LIB}
${RM} main.o class.o
and then my compiling command seems to be mpicxx -o myProgram main.o class.o /usr/bin/ar/ libclassdll.a class.o -L ( a lot of linking here ) and at least it says: g++ classdll.a no such a file or dir.
然后我的编译命令似乎是 mpicxx -o myProgram main.o class.o /usr/bin/ar/libclassdll.a class.o -L（这里有很多链接），至少它说：g++ classdll.a没有这样的文件或目录。
So it doesn't generate even a lib file for me. So any ideas will be really appreciated.
所以它甚至不会为我生成一个 lib 文件。所以任何想法都将不胜感激。
A new problem when I uploaded makefile on the different machine, my current makefile looks like this
我在另一台机器上上传 makefile 时出现的新问题，我当前的 makefile 看起来像这样
LibMyClass.so: MyClass.o chkopts
-${CLINKER} -shared -Wl,-soname,${SONAME} -o ${VERS} *.o ${PETSC_MAT_LIB}
mv ${VERS} ${LIBADD}
ln -sf ${LIBADD}${VERS} ${LIBADD}${SOWOV}
ln -sf ${LIBADD}${VERS} ${LIBADD}${SONAME}
That works on one machine but other machine gives following error
这适用于一台机器，但另一台机器出现以下错误
/usr/bin/ld: MyClass.o: relocation R_X86_64_32S against `.rodata' can not be used when making a shared object; recompile with -fPIC
MyClass.o: could not read symbols: Bad value
I did change the paths of course but I guess that indicates other kind of problem because even if I type "g++ -shared -Wl,-soname,libmyclass.so.1 -o libmyclass.so.1.0 MyClass.o" or "g++ -fPIC -share... " I'll get the same error.
当然，我确实更改了路径，但我想这表明存在其他类型的问题，因为即使我输入“g++ -shared -Wl,-soname,libmyclass.so.1 -o libmyclass.so.1.0 MyClass.o”或“g++” -fPIC -share...” 我会得到同样的错误。
回答by Beta
Ideally you should construct the library first, then use it, just as you would "by hand".
理想情况下，您应该先构建库，然后使用它，就像“手动”一样。
To construct (or update) the library, you need a rule something like this:
要构建（或更新）库，您需要一个类似这样的规则：
libclassdll.a: class.o
ar -rv libclassdll.a class.o
Or more concisely, like this:
或者更简洁地说，像这样：
libclassdll.a: class.o
ar $(ARFLAGS) $@ $^
Then the rule for myProgrambecomes:
那么规则myProgram变为：
# Assuming CLINKER is something civilized, like gcc
myProgram: main.o libclassdll.a chkopts
-${CLINKER} -o myProgram main.o -L. -lclassdll ${PETSC_MAT_LIB}
or better:
或更好：
myProgram: main.o libclassdll.a chkopts
-${CLINKER} -o $@ $< -L. -lclassdll ${PETSC_MAT_LIB}
So in your makefile, you would replace
所以在你的 makefile 中，你会替换
myProgram: main.o class.o chkopts
-${CLINKER} -o myProgram main.o class.o ${PETSC_MAT_LIB}
${RM} main.o class.o
with
和
myProgram: main.o libclassdll.a chkopts
-${CLINKER} -o $@ $< -L. -lclassdll ${PETSC_MAT_LIB}
libclassdll.a: class.o
ar $(ARFLAGS) $@ $^
There are other refinements you can make, but that should be enough for now.
您还可以进行其他改进，但现在应该足够了。
回答by Kaz
Make myProgram depend on main.o and on the libclass.a (don't call it libclassdll.a; it is not a DLL, but a static library).
让 myProgram 依赖于 main.o 和 libclass.a（不要称它为 libclassdll.a；它不是一个 DLL，而是一个静态库）。
General gist of the solution:
解决方案的一般要点：
# $@ means "the target of the rule"
# $^ means "the prerequisites: main.o and libclass.a"
myProgram: main.o libclass.a
$(CC) -o $@ $^ # additional arguments for other libraries, not built in this make
libclass.a: class.o
# your $(AR) command goes here to make the library
