rspec/rules/S5485/cfamily/rule.adoc

== Why is this an issue?

The standard C library includes a number of functions for handling streams. If not called correctly, these functions can have undefined behavior. More specifically:

* ``++FILE*++`` should be checked for null before being used in a function that accesses the file content
* The third argument of ``++fseek++`` must be ``++SEEK_SET++``, ``++SEEK_END++``, or ``++SEEK_CUR++``


=== Noncompliant code example

[source,cpp]
----
FILE *file1 = fopen("myFile", "r");
fseek(file1, 1, SEEK_SET); // Noncompliant, file could be NULL
fclose(file1);

FILE *file2 = tmpfile();
ftell(file2); // Noncompliant, file could be NULL
if (file2) {
  fseek(file2, 1, 3); // Noncompliant, third argument should either be SEEK_SET, SEEK_CUR or SEEK_END
}
fclose(file2);
----


=== Compliant solution

[source,cpp]
----
FILE *file1 = fopen("myFile", "r");
if (file1) {
  fseek(file1, 1, SEEK_SET);
  fclose(file1);
}

FILE *file2 = tmpfile();
if (file2) {
  ftell(file2);
  fseek(file2, 1, SEEK_END);
  fclose(file2);
}
----


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