Task: Linking a Single File
Access the directory tasks/single-link/support/example/. We want to follow the linking commands for a single C source file. The source file is hello.c.
In the three subdirectories, you will find support files for the following scenarios:
a-dynamic/: creating a dynamic executable fileb-static/: creating a static executable filec-standalone/: creating a standalone executable file without the standard C library
In each subdirectory, we use the make command to compile the executable file hello. We use the command file hello to check whether the file is compiled dynamically or statically.
In the Makefile files, the linking command uses gcc. An equivalent command that directly uses ld is commented out. To track the direct usage of ld, we can comment out the gcc command and uncomment the ld command.
In the case of c-standalone/, since we are not using the standard C library or C runtime library, we need to replace their functionalities. The functionalities are replaced in the start.asm and puts.asm files. These files implement the _start function/symbol and the puts function, respectively. The _start function/symbol is, by default, the entry point of an executable program. The _start function is responsible for calling the main function and terminating the program. Because there is no standard library, these two files are written in assembly language and use system calls.
Bonus: Add a command in the Makefile in the c-standalone/ directory that explicitly uses ld for linking.
Access the directory tasks/single-link/support/diy/. We want to compile and link the source files in each subdirectory, following the model of the previous exercise.
Copy the Makefile files and update them in each subdirectory to obtain the executable file.
If you’re having difficulties solving this exercise, go through this reading material.