[PATCH] D152436: [clang][analyzer] Move checker alpha.unix.StdCLibraryFunctions out of alpha.

[Balázs Kéri via Phabricator via cfe-commits]

balazske added a comment.

It is possible to add note tags to show decisions at standard functions. For example at `fileno` show if it has failed or not failed. The most simple way is to add it to all places, this means a note will show up on any bug path at all standard function usages. This is how it works already with the existing notes. Like in the following code:

  int __test_case_note();
  
  int test_case_note_1(int y) {
    int x1 = __test_case_note(); // expected-note{{Function returns 1}}
    int x = __test_case_note(); // expected-note{{Function returns 0}} \
                                // expected-note{{'x' initialized here}}
    return y / x; // expected-warning{{Division by zero}} \
                  // expected-note{{Division by zero}}
  }
  
  int test_case_note_2(int y) {
    int x = __test_case_note(); // expected-note{{Function returns 1}}
    return y / (x - 1); // expected-warning{{Division by zero}} \
                        // expected-note{{Division by zero}}
  }

Here the first note at line with "x1" is not necessary. This problem can be fixed if the note is only shown when the return value is "interesting":

  int __test_case_note();
  
  int test_case_note_1(int y) {
    int x1 = __test_case_note(); // no note
    int x = __test_case_note(); // expected-note{{Function returns 0}} \
                                // expected-note{{'x' initialized here}}
    return y / x; // expected-warning{{Division by zero}} \
                  // expected-note{{Division by zero}}
  }
  
  int test_case_note_2(int y) {
    int x = __test_case_note(); // no note
    return y / (x - 1); // expected-warning{{Division by zero}} \
                        // expected-note{{Division by zero}}
  }

But in this case the note at `test_case_note_2` disappears because `x-1` is interesting, but not `x`. Fixing this problem looks more difficult.

>From these two solutions, which one is better? (Show many unnecessary notes, or show only necessary ones but lose some of the useful notes too.)


Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D152436/new/

https://reviews.llvm.org/D152436