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Suppose that you are give a single C source file, that contains a max. of 300 lines of code.
Suppose also that the file, while implementing several functions, DOES NOT contain the character '#' in it (meaning, there are NO #include statmements, and no other statements that have '#' in the file).
My question is, does the above guarantee that the file does not do any I/O? does it guarantee that the file will not be able to (say) erase the contents of the hard drive, or do other fishy things?
(I am supposed to get 100-200 single C files, that (as mentioned) do not include the char # in them. I was asked to write a simple program that will programmatically check if a single C source file with no # is potentially involved in I/O, accessing to the network etc).
Given the fact that no statements with # are allowed -- what is the WORST code a coder can include in such a C file to potentially damage the system of the one who runs it?
I know that no check will yield 100% accuracy -- but am interested at least to do some basic checks that will raise a red flag if some expressions / keywords are found. Any ideas of what to look for?
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Address in CIf you have a variable var in your program, &var will give you its address in the memory. We have used address numerous times while using the scanf() function. scanf("%d", &var); Here, the value entered by the user is stored in the address of var variable. Let's take a working example.
Archive libraries (. a) are statically linked i.e when you compile your program with -c option in gcc. So, if there's any change in library, you need to compile and build your code again.
An O file is a compiled C program object. Some C compilers create O files during the executable (. EXE) creation process. O files themselves are typically not executable. When compiling a C program, compilers first transform all the program's source code files into compiled object files.
For C File I/O you need to use a FILE pointer, which will let the program keep track of the file being accessed. For Example: FILE *fp; To open a file you need to use the fopen function, which returns a FILE pointer.
No, it can't guarantee that. You can produce the code where all includes and macros are expanded, and you can make it into a single huge file, then compile it... that file, won't contain any preprocessor directive, though it can do anything usually C can do on a system.
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If the original coder were to include inline assembly, they could do pretty much anything they liked, without importing any libraries.
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