Bug #15299: hash.c: warning: ‘bin’ may be used uninitialized in this function

• Status: Closed
• Assignee: nobu (Nobuyoshi Nakada)
• Target version: -
• ruby -v: ruby 2.6.0dev (2018-12-09 trunk 66296) [x86_64-linux]
• Backport: 2.3: UNKNOWN, 2.4: UNKNOWN, 2.5: UNKNOWN

[duerst (Martin Dürst)]

When compiling the latest version of trunk, I get some warnings in hash.c, as follows:

compiling hash.c
hash.c: In function ‘linear_update’:
hash.c:849:24: warning: ‘bin’ may be used uninitialized in this function [-Wmaybe-uninitialized]
             clear_entry(RHASH_ARRAY_REF(hash, bin));
                        ^
hash.c: In function ‘rb_hash_stlike_update’:
hash.c:849:24: warning: ‘bin’ may be used uninitialized in this function [-Wmaybe-uninitialized]
hash.c:811:14: note: ‘bin’ was declared here
     unsigned bin;
              ^

This warning appeared already when I reported issue #15279, but I didn't mention it because I hoped it would also disappear when #15279 was fixed.

[nobu (Nobuyoshi Nakada)]

What version of cc?

It is a false warning.

bin is initialized if the hash is not empty, and otherwise existing is FALSE.
And the line is in a block of if (existing), so unintialized bin never reaches there.

[duerst (Martin Dürst)]

nobu (Nobuyoshi Nakada) wrote:

What version of cc?

[duerst@stazersee ruby2]$ gcc --version
gcc (GCC) 4.8.3 20140911 (Red Hat 4.8.3-7)

[duerst (Martin Dürst)]

• ruby -v changed from ruby 2.4.0dev (2016-06-09 trunk 55334) [x86_64-linux] to ruby 2.6.0dev (2018-12-09 trunk 66296) [x86_64-linux]

[nobu (Nobuyoshi Nakada)]

• Status changed from Open to Closed

Applied in changeset trunk|r66306.

---

Initialize bin

• hash.c (linear_update): initialize bin just to silence false
  warnings by old gcc 4.8. [Bug #15299]