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How can Coccinelle assist in substituting a function with arguments that vary in number?

asked 2021-08-06 11:00:00 +0000

nofretete gravatar image

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answered 2023-01-06 13:00:00 +0000

ladyg gravatar image

Coccinelle can assist in substituting a function with arguments that vary in number by using its semantic patch syntax.

First, the semantic patch needs to specify the function that should be substituted and the target function that should replace it. This can be done using the following syntax:

@@
expression F;
@@

@@
expression T;
@@

@@
F(...)
{
  // body of the original function
}
@@

@@
T(...)
{
  // body of the target function
}
@@

In the above example, F represents the original function that needs to be replaced and T represents the target function that will replace it.

Next, the semantic patch needs to take into account the varying number of arguments in the function. This can be done using the ellipsis ... syntax, which represents a variable number of arguments.

For example, if the original function had three arguments, the semantic patch would look like this:

@@
expression F;
@@

@@
expression T;
@@

@@
F(arg1, arg2, arg3)
{
  // body of the original function
}
@@

@@
T(...)
{
  // example function with varying number of arguments
  if (argc == 1) {
    // function body for one argument
  } else if (argc == 2) {
    // function body for two arguments
  } else {
    // function body for more than two arguments
  }
}
@@

In this example, argc refers to the number of arguments passed to the target function. By using conditional statements, the target function can adjust its behavior based on the number of arguments passed to it.

Once the semantic patch is written, it can be applied to the code using the spatch command:

spatch -sp_file patch.cocci file.c

This will substitute all occurrences of the original function with the target function, taking into account the varying number of arguments.

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Asked: 2021-08-06 11:00:00 +0000

Seen: 12 times

Last updated: Jan 06 '23