C / C++ implement and pass code [duplicate] - c++

Question

This question already has answers here:
String literals C++?
(4 answers)
Closed 9 years ago.
I have interpreter from another language in C. I have to pass code (about 200 lines) from another language to this interpreter and here problem occur.
char* command_line[] = {
"",
"-e",
"print \"Hello from C!\\n\";"
};
This code is parse by:
(..)
parser(my_p, NULL, 3, command_line, (char **)NULL);
(...)
In code abobe I use array but even simple code have to be wrapped with \ before chars like " ; | \ etc.
How to avoid this problem and pass more then 200 multi row lines of code comfortable?

Answer 1

If you are using C++11, you can use raw string literals.
R"(print "Hello from C!\n";)"
Or you can simply put all the data into an external file and just read it on start. No need to escape any data there.

Answer 2

You could use the C preprocessor to do the stringification for you:
#define STRINGIFY(...) #__VA_ARGS__
#define STRINGIFY_NL(...) #__VA_ARGS__ "\n"
char* command_line[] = {
"",
"-e",
STRINGIFY(print "Hello from C!\n";), //< one element of the array
//< another element of the array
//< with embedded NL
STRINGIFY_NL(print "Hello from C!") //< no comma and the next line is glued
STRINGIFY ("for a second time";), //< end of other string
};
The only restrictions to observe would be that possible () have to balance inside the argument to STRINGIFY and that you'd have to place the macro on each line that you want to escape.

Answer 3

Unfortunately there is no support for literal strings or similar useful constructs in C, so if you want to write the interpreted code inside your C program you will have to be careful and escape quotes and slashes as you have stated.
The alternative is to write the code into a text file and treat it as an external resource file. You can read the resource file from inside your code into a string and then pass that to parser().
The ease of this depends on the platform you are using. Windows has good support for resource files and embedding them in to .exe files. I am sure it is possible with gcc too, but I haven't done it before. A bit vague I'm afraid, but I hope it helps.

Answer 4

You can use a script to take your text input, as a file, and stringify it (escaping double-quotes and newlines):
#!/usr/bin/env python
import sys
def main(argv = None):
if argv is None:
argv = sys.argv
if len(argv) < 2:
sys.stderr.write("Usage: stringify.py input.txt [... input.txt]\n")
sys.exit(1)
i = 1
while i < len(argv):
inname = argv[i]
firstline = True
try:
infile = open(inname, "r")
for line in infile:
line = line.replace('"', '\\"').replace('\n', '\\n')
sys.stdout.write('"{0}"\n'.format(line))
except IOError, msg:
sys.stderr.write("exception {0}\n".format(msg))
return 2
i = i + 1
return 0
if __name__ == "__main__":
sys.exit(main())