GCC argument descriptor
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Problem 4. GCC argument descriptor
Problem background
To compile C/C++ code, we need to execute a command that calls the compiler with some arguments. For example:
gcc hello.c -o hello.exe -std=c17 -Wall -Wpedantic -Wextra
This command compiles the C source code file hello.c with gcc, setting the output file to be hello.exe, setting the language standard to be ISO C17, and enabling some kinds of warnings and errors by -Wall -Wpedantic -Wextra.
Taking a look at GCC's manual, you will find an overwhelmingly long list of supported arguments. Is there a tool that can generate some explanations of the arguments, or at least for some of the most common ones? For example, suppose the name of that tool is gcc_descriptor.exe (without .exe on Mac OS X and Linux). It would be helpful if the following command (with .\ replaced by ./ on Mac OS X and Linux)
.\gcc_descriptor hello.c -o hello.exe -std=c17 -Wall -Wpedantic -Wextra
could print
hello.c: C source code as input file.
-o hello.exe: Place the primary output in file hello.exe.
-std=c17: Set the language standard to ISO C17.
-Wall: Enable all the warnings about constructions that some users consider questionable, and that are easy to avoid (or modify to prevent the warning).
-Wpedantic: Issue all the warnings demanded by strict ISO C and ISO C++ and reject all programs that use forbidden extensions.
-Wextra: Enable some extra warning flags that are not enabled by -Wall.
Your task is to implement such a tool that generates explanations for some very common GCC arguments.
Problem description
Write a program that accepts command-line arguments, which are the arguments that we want to pass to GCC, and print the descriptions for them.
The supported kinds of arguments are as follows.
1. -Wall
Description:
-Wall: Enable all the warnings about constructions that some users consider questionable, and that are easy to avoid (or modify to prevent the warning).
2. -Wpedantic
Description:
-Wpedantic: Issue all the warnings demanded by strict ISO C and ISO C++ and reject all programs that use forbidden extensions.
3. -Wextra
Description:
-Wextra: Enable some extra warning flags that are not enabled by -Wall.
4. -Werror
Description:
-Werror: Make all warnings into errors.
5. -o xxx
Description:
-o xxx: Place the primary output in file xxx.
where xxx is replaced by the actual file name (see the example below). Note that this option consists of two arguments, where the first one is -o and the second one is the file name.
6. -I xxx
Description:
-I xxx: Add the directory xxx to the list of directories to be searched for header files during preprocessing.
where xxx is replaced by the actual directory name (see the example below). Note that this option consists of two arguments, where the first one is -I and the second one is the directory name.
7. -std=xxx
Description:
-std=xxx: Set the language standard to yyy.
where xxx is replaced by the actual value (see the example below) and yyy is replaced by the name of the standard according to the following table.
xxx |
yyy |
example | example output |
|---|---|---|---|
cN |
ISO CN |
c17 |
ISO C17 |
c++N |
ISO C++N |
c++20 |
ISO C++20 |
gnuN |
GNU dialect of CN |
gnu11 |
GNU dialect of C11 |
gnu++N |
GNU dialect of C++N |
gnu++14 |
GNU dialect of C++14 |
N consists of two digits. For example, the 2003 ISO C++ standard is named C++03.
8. Other
Anything that does not match the patterns above is treated as an input file.
Description:
xxx: yyy as input file.
where xxx is replaced by the file name and yyy is replaced by the type of the file according to the following table.
xxx |
yyy |
example |
|---|---|---|
*.c |
C source code |
hello.c |
*.h |
C/C++ header file |
stdio.h |
*.cpp, *.C, *.cc, *.cxx |
C++ source code |
checker.cc, game.cpp |
*.hpp, *.hxx |
C++ header file |
utils.hpp |
Notes
There is no input for this problem. The arguments to be explained are given as the command line arguments of your program.
It is guaranteed that the arguments are valid: Anything that does not match the patterns in 1 ~ 7 must be a valid C/C++ source or header file name as described in the table above. For the language standards (pattern 7), you don't need to check whether the standard that it refers to actually exists. Things like -std=c++100000 won't appear.
The names of the files and directories involved in the arguments do not contain whitespaces or quotes.
The name following -o or -I is not a C/C++ source or header file.
Print the explanations in order of the arguments.
Please be extremely careful about the output contents, especially the spaces, newlines and punctuations.
Example
Suppose the name of your program (executable) is my_program.exe (without .exe on Mac OS X and Linux). If the following command (with .\ replaced by ./ on Mac OS X and Linux) is executed,
.\my_program -std=c++20 -Wall -Wpedantic -Wextra a.c b.hxx c.cpp -Werror -o output_file -I /usr/local/boost_1_80_0/
the output is
-std=c++20: Set the language standard to ISO C++20.
-Wall: Enable all the warnings about constructions that some users consider questionable, and that are easy to avoid (or modify to prevent the warning).
-Wpedantic: Issue all the warnings demanded by strict ISO C and ISO C++ and reject all programs that use forbidden extensions.
-Wextra: Enable some extra warning flags that are not enabled by -Wall.
a.c: C source code as input file.
b.hxx: C++ header file as input file.
c.cpp: C++ source code as input file.
-Werror: Make all warnings into errors.
-o output_file: Place the primary output in file output_file.
-I /usr/local/boost_1_80_0/: Add the directory /usr/local/boost_1_80_0/ to the list of directories to be searched for header files during preprocessing.