Fix missing compiler macros in cppcheck analysis

[willy-liu]

Static analysis with cppcheck fails because predefined compiler macros are not available during analysis. This causes the environment detection in the list macro to fall back to an invalid code branch, triggering false errors such as unused labels.

Although this fallback branch is not used in supported environments, it is still parsed by cppcheck unless the proper macro definitions are provided.

This commit resolves the issue by passing the necessary compiler environment macros to cppcheck through the -D option, ensuring correct evaluation of conditional logic in macro definitions.

• Prevent static analysis false positives in list macros
• Ensure the environment is correctly simulated during checks

See https://hackmd.io/@willy-liu/linux2025-homework1#q_free for details.

Change-Id: If8b51c44f194f19f109bc4aaf91a464f850e7fdc

[willy-liu]

Refactored the detection of compiler type and standard version
into a Bash function.

The function get_compiler_macros
determines the compiler in use, extracts the
standard version, and constructs the necessary macro definitions
for static analysis tools. The detected macros are then passed
to cppcheck to ensure proper environment simulation.

• Improve code organization and clarity
• Ensure static analysis tools receive accurate macro definitions
• Support both GCC and Clang detection

[willy-liu]

Standardize naming and indentation

Renamed function for consistency and adjusted indentation to align with
project style.

[jserv]

During the make process, compilation utilizes the cc command, which references either gcc or clang based on your system's configuration. On GNU/Linux systems, cc typically defaults to gcc, while BSD systems (including macOS) link cc to clang. We shall analyze the cc command before directly invoking either gcc or clang.

See also: https://github.com/sysprog21/rv32emu/blob/master/mk/toolchain.mk

[willy-liu]

After learning the cc command, I understand it’s a better way to identify the C compiler.

However, when I checked the Makefile, I noticed that make defaults to gcc because CC = gcc is set in the first line.

https://github.com/sysprog21/lab0-c/blob/master/Makefile

[jserv]

I noticed that make defaults to gcc because CC = gcc is set in the first line.

The build compiler and configurations can be checked by examining the cc variable, as the CC variable may be subject to override. It's generally acceptable to do this verification.

[willy-liu]

Refactored the function using cc to check compiler type.

[jserv]

Thank @willy-liu for contributing!