Check for invalid digits when parsing octal constants

[DrXiao]

After introducing the pull request (#151 ), I use the following code to test the parser:

/* test.c */
int main() {
    int a = 03, b = 01118, c = 091;
    printf("%d %d %d\n", a, b, c); 
    return 0;
}

$ qemu-arm out/shecc-stage2.elf -o test test.c
$ qemu-arm test
3 592 73

Obviously, the octal numbers (01118 and 091) are invalid but the parser doesn't check whether they are valid or not.

Thus, the pull request improves the parser to enhance the validation check.

[fennecJ]

The check for c < '0' is redundant because the loop will exit as soon as is_digit() in line 642 returns false.
For example, consider the case int a = 0.; funct(a);, where the ASCII value of '.' is less than '0'.
On the first iteration, c = token[i++] assigns c the value '0' and increments i to 1.
Then, the check in the while loop at line 642 is_digit(token[i = 1]) will become is_digit('.') and return false, causing the loop to exit.
As a result, the check for c < '0' is never triggered when the comming digit is less then '0'.

[DrXiao]

@fennecJ , yes, here doesn't need to check for c < '0'. Thank you for your feedback, I will improve it later.

[ChAoSUnItY]

Please also add your code to the test suite for code validation.

[DrXiao]

The proposed changes let shecc generate a compilation error message when parsing invalid octal numbers.

However, originally, tests/driver.sh only compiles valid C programs and checks the exit code or standard output, and the test suite has never compiled any invalid C program before.

This is the first instance of adding an invalid C program, which includes some invalid octal constants, to test/driver.sh to check whether (native) shecc generates the error message or not.

Thus, I will add a new function called try_compile_error() to the test suite, and the function will accept an invalid C program and then check if the exit code returned by shecc is a non-zero value. Eventually, the test suite will have the ability to test invalid C programs.

function try_compile_error() {
    local input=$(cat)

    local tmp_in="$(mktemp --suffix .c)"
    local tmp_exe="$(mktemp)"
    echo "$input" > "$tmp_in"
    "$SHECC" -o "$tmp_exe" "$tmp_in"
    local exit_code=$?

    if [ 0 == $exit_code ]; then
        echo "Error: compilation is passed"
        exit 1
    fi
}


# ...

try_compile_error << EOF
int main() {
    int a = 03, b = 01118, c = 091;
    printf("%d %d %d\n", a, b, c); 
    return 0;
}
EOF

[jserv]

Thank @DrXiao for contributing!