"CMake Build in Action" - Build Journey

小麦克

"CMake Build in Action" - Build Journey [Copy link]

# Build Journey I have received "CMake Build Practice" for two days and started to learn. I have also been exposed to CMake development in my daily work. For example, QT6 began to recommend the use of CMake for building. I have also done several QT CMake-related projects, but the project templates are all automatically generated by the tool, and the project changes are not big. I don't understand the internal principles of CMake, and I don't know how to start when I encounter problems. I am very grateful to the forum for providing me with this opportunity. Later, I will study and improve together with the forum friends. ### Build Journey The first chapter starts with the basics of building, so that we can understand the principles of building. The book explains Windows and Linux separately, but the principles are similar. Since I am learning Linux recently and am more familiar with the Linux development environment, I will test it in the Linux environment later, and I only need to understand the Windows and macOS environments. #### 1. Static library Static library (static library), also known as statically-linked library. The static library contains all target files and some symbol indexes. When our program links to a static library, all the required functions, variables and other target codes will be copied to our program, and we no longer need to bring these static libraries when publishing the program. The advantage is that there is no dependency problem when the program is running, but the disadvantage is that the size of our program will increase. According to the examples in the book, create the following files```bash bruce@ubuntu:~/Documents/study/cmake/001$ tree . ├── ac ├── bc ├── libab.h ├── main.c └── Makefile 1 directory, 5 files ``` For the convenience of testing, the `clean` target is added in `Makefile````makefile main: main.o libab.a gcc main.o -o main -L. -lab main.o: main.c gcc -c main.c -o main.o libab.a: ao bo ar rcs libab.a ao bo ao: ac gcc -c ac -o ao bo: bc gcc -c bc -o bo .PHONY: clean clean: rm -rf *.o *.a main ``` Test, you can see that the static library file `libab.a` is generated ```bash bruce@ubuntu:~/Documents/study/cmake/001$ make gcc -c main.c -o main.o gcc -c ac -o ao gcc -c bc -o bo ar rcs libab.a ao bo gcc main.o -o main -L. -lab bruce@ubuntu:~/Documents/study/cmake/001$ tree . ├── ac ├ ── ao ├── bc ├── bo ├── libab.a ├── libab.h ├── main ├── main.c ├── main.o └── Makefile 1 directory, 10 files bruce@ubuntu:~/Documents/study/cmake/001$ ls -alh Total 60K drwxrwxr -x 2 bruce bruce 4.0K Sep 6 11:33 . drwxrwxr-x 3 bruce bruce 4.0K Sep 6 11:30 .. -rw-rw-r-- 1 bruce bruce 54 Sep 6 11:12 ac -rw-rw-r-- 1 bruce bruce 1.5K Sep 6 11:33 ao -rw -rw-r-- 1 bruce bruce 54 Sep 6 11:13 bc -rw-rw-r-- 1 bruce bruce 1.5K Sep 6 11:33 bo -rw-rw-r-- 1 bruce bruce 3.1K Sep 6 11:33 libab.a -rw-rw-r-- 1 bruce bruce 81 S ep 6 11:15 libab.h -rwxrwxr-x 1 bruce bruce 16K Sep 6 11:33 main -rw-rw-r-- 1 bruce bruce 82 Sep 6 11:16 main.c -rw-rw-r-- 1 bruce bruce 1.4K Sep 6 11:33 main.o -rw-rw-r-- 1 bruce bruce 236 Sep 6 11:28 Makefile bruce@ubuntu:~/Documents/study/cmake/001$ ./main a b bruce@ubuntu:~/Documents/study/cmake/001$ ``` Copy main to other directories and it can be executed without bringing `libab.a` #### 2. Dynamic library Dynamic library (dynamic A dynamic library is also called a dynamically-linked library (DLL) or a shared library. Unlike a static library, the object code of a dynamic library is dynamically linked when the program is downloaded or run. The advantage is that it is decoupled from the program and can be updated separately, and the size of our application will not increase. The disadvantage is that over time, the application may become incompatible with the dynamic library, which is a disaster for the final target customer. Copy the previous 001 folder to 002, modify `Makefile` ```bash main: main.o libab.so gcc main.o -o main -L. '-Wl,-R$$ORIGIN' -lab main.o: main.c gcc -c main.c -o main.o libab.so: ao bo gcc -shared ao bo -o libab.so ao: ac gcc -c ac -o ao bo: bc gcc -c bc -o bo .PHONY: clean clean: rm -rf *.o *.so main ``` The main change is the `libab.so` generation method: `gcc -shared ao bo -o libab.so` Note that `'-Wl,-R$$ORIGIN'' needs to be added to generate `main`, otherwise an error will occur `./main: error while loading shared libraries: libab.so: cannot open shared object file:No such file or directory` #### 3. Reference third-party libraries One of the great advantages of C and C++ programming is the rich ecosystem, which allows us to stand on the shoulders of giants. Learn how to reference the third-party `Boost` library. : Download boost library and unzip it to `~/boost` ```bash cd ~ wget https://archives.boost.io/release/1.86.0/source/boost_1_86_0.tar.gz tar -xf boost_1_86_0.tar.gz boost ``` Create `main.cpp` and `Makefile`, compile and test```bash bruce@ubuntu:~/Documents/study/cmake/003$ tree . ├── main ├── main.cpp └── Makefile 1 directory, 3 files bruce@ubuntu:~/Documents/study/cmake/003$ cat Makefile main: main.cpp g++ main.cpp -I ~/boost -o main clean: rm main bruce@ubuntu:~/Documents/study/cmake/003$ cat main.cpp #include<boost algorithm="" string.hpp=""> #include <iostream> using namespace std; using namespace boost; int main(void) { string str = " hello world!"; cout << str << endl; to_upper(str); cout << str << endl; trim(str); cout << str << endl; return 0; } bruce@ubuntu:~/Documents/study/cmake/003$ ``` Here we only reference the hpp header file and do not need to link the boost library. Let's see how to link the boost c++ library. Since the boost library is very large, we will directly install the precompiled boost library for testing. ```bash sudo apt install libboost-all-dev ``` Create test project 004 ```bash bruce@ubuntu:~/Documents/study/cmake/004$ tree . ├── main.cpp ├── Makefile ├── shared_boost └── static_boost 1 directory, 4 files bruce@ubuntu:~/Documents/study /cmake/004$ cat main.cpp #include<boost regex.hpp=""> #include<iostream> using namespace std; using namespace boost; int main(void) { string s = R"( "Search Engines: http://baidu.com https://google.com About me: https://hello.com/world" )"; regex e(R"(([a-zA-Z]*)://[a-zA-Z0-9./]+)"); for (sregex_iterator m(s.begin(), s.end(), e), end; m != end; ++m) { cout << "URL: " << (*m)[0].str() << endl; cout << "Scheme: " <<(*m)[1].str() << endl; cout << endl; } return 0; } bruce@ubuntu:~/Documents/study/cmake/004$ cat Makefile all: static_boost shared_boost static_boost: main.cpp g++ main.cpp $(CXXFLAGS) $(LDFLAGS) -l:libboost_regex.a -o static_boost shared_boost: g++ main.cpp $(CXXFLAGS) $(LDFLAGS) -lboost_regex -o shared_boost clean: rm *_boost bruce@ubuntu:~/Documents/study/cmake/004$ ls -alh 总计 1.4M drwxrwxr-x 2 bruce bruce 4.0K Sep6 16:11 . drwxrwxr-x 6 bruce bruce 4.0K Sep6 15:49 .. -rw-rw-r-- 1 bruce bruce480 Sep6 16:10 main.cpp -rw-rw-r-- 1 bruce bruce233 Sep6 16:02 Makefile -rwxrwxr-x 1 bruce bruce 708K Sep6 16:10 shared_boost -rwxrwxr-x 1 bruce bruce 708K Sep6 16:10 static_boost ``` 这里测试感觉不成功，因为生成的 `shared_boost` 和 `static_boost` 大小一样，通过`readelf`读取的动态库也一样。 ```bash bruce@ubuntu:~/Documents/study/cmake/004$ readelf -d ./static_boost Dynamic section at offset 0x5d9d0 contains 29 entries: 标记 类型 名称/值 0x0000000000000001 (NEEDED) 共享库：[libstdc++.so.6] 0x0000000000000001 (NEEDED) 共享库：[libgcc_s.so.1] 0x0000000000000001 (NEEDED) 共享库：[libc.so.6] 0x000000000000000c (INIT) 0x7000 0x000000000000000d (FINI) 0x44f70 0x0000000000000019 (INIT_ARRAY) 0x5ddb0 0x000000000000001b (INIT_ARRAYSZ) 8 (bytes) 0x000000000000001a (FINI_ARRAY) 0x5ddb8 0x000000000000001c (FINI_ARRAYSZ) 8 (bytes) 0x000000006ffffef5 (GNU_HASH) 0x3b0 0x0000000000000005 (STRTAB) 0x12e0 0x0000000000000006 (SYMTAB) 0x410 0x000000000000000a (STRSZ) 7434 (bytes) 0x000000000000000b (SYMENT) 24 (bytes) 0x0000000000000015 (DEBUG) 0x0 0x0000000000000003 (PLTGOT) 0x5ebe0 0x0000000000000002 (PLTRELSZ) 2856 (bytes) 0x0000000000000014 (PLTREL) RELA 0x0000000000000017 (JMPREL) 0x60e0 0x0000000000000007 (RELA) 0x3248 0x0000000000000008 (RELASZ) 11928 (bytes) 0x0000000000000009 (RELAENT) 24 (bytes) 0x000000000000001e (FLAGS) BIND_NOW 0x000000006ffffffb (FLAGS_1) 标志： NOW PIE 0x000000006ffffffe (VERNEED) 0x3128 0x000000006fffffff (VERNEEDNUM) 3 0x000000006ffffff0 (VERSYM) 0x2fea 0x000000006ffffff9 (RELACOUNT) 447 0x0000000000000000 (NULL) 0x0 bruce@ubuntu:~/Documents/study/cmake/004$ readelf -d ./shared_boost Dynamic section at offset 0x5d9d0 contains 29 entries: 标记 类型 名称/值 0x0000000000000001 (NEEDED) 共享库：[libstdc++.so.6] 0x0000000000000001 (NEEDED) 共享库：[libgcc_s.so.1] 0x0000000000000001 (NEEDED) 共享库：[libc.so.6] 0x000000000000000c (INIT) 0x7000 0x000000000000000d (FINI) 0x44f70 0x0000000000000019 (INIT_ARRAY) 0x5ddb0 0x000000000000001b (INIT_ARRAYSZ) 8 (bytes) 0x000000000000001a (FINI_ARRAY) 0x5ddb8 0x000000000000001c (FINI_ARRAYSZ) 8 (bytes) 0x000000006ffffef5 (GNU_HASH) 0x3b0 0x0000000000000005 (STRTAB) 0x12e0 0x0000000000000006 (SYMTAB) 0x410 0x000000000000000a (STRSZ) 7434 (bytes) 0x000000000000000b (SYMENT) 24 (bytes) 0x0000000000000015 (DEBUG) 0x0 0x0000000000000003 (PLTGOT) 0x5ebe0 0x0000000000000002 (PLTRELSZ) 2856 (bytes) 0x0000000000000014 (PLTREL) RELA 0x0000000000000017 (JMPREL) 0x60e0 0x0000000000000007 (RELA) 0x3248 0x0000000000000008 (RELASZ) 11928 (bytes) 0x0000000000000009 (RELAENT) 24 (bytes) 0x000000000000001e (FLAGS) BIND_NOW 0x000000006ffffffb (FLAGS_1) 标志： NOW PIE 0x000000006ffffffe (VERNEED) 0x3128 0x000000006fffffff (VERNEEDNUM) 3 0x000000006ffffff0 (VERSYM) 0x2fea 0x000000006ffffff9 (RELACOUNT) 447 0x0000000000000000 (NULL) 0x0 ``` 有空好好研究研究。。。 </iostream></boost></iostream></boost>

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13620203064 Posted on 2024-9-6 17:20 Do you have a pdf document or e-book content? Please send me a link.

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