[Bug analyzer/105273] New: -Wanalyzer-use-of-uninitialized-value warns on "missing" default for switch when callers can be statically determined

["avarab at gmail dot com" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105273

            Bug ID: 105273
           Summary: -Wanalyzer-use-of-uninitialized-value warns on
                    "missing" default for switch when callers can be
                    statically determined
           Product: gcc
           Version: 12.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: analyzer
          Assignee: dmalcolm at gcc dot gnu.org
          Reporter: avarab at gmail dot com
  Target Milestone: ---

Created attachment 52807
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=52807&action=edit
test case with an enum

With GCC 12.0 built from c1ff207af66 (ppc: testsuite: skip pr60203 on no
ldbl128, 2022-04-12) I get a warning on the attached test case:

 gcc -fanalyzer analyze.c
analyze.c: In function ‘vreportf’:
analyze.c:28:17: warning: use of uninitialized value ‘pfx’ [CWE-457]
[-Wanalyzer-use-of-uninitialized-value]
   28 |                 snprintf(buf, sizeof(buf), "%s", pfx);
      |                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  ‘vreportf’: events 1-6
    |
    |   13 |         const char *pfx;
    |      |                     ^~~
    |      |                     |
    |      |                     (1) region created on stack here
    |   14 | 
    |   15 |         switch (kind) {
    |      |         ~~~~~~       
    |      |         |
    |      |         (2) following ‘default:’ branch...
    |......
    |   25 |         if (kind == USAGE_BUG)
    |      |            ~         
    |      |            |
    |      |            (3) ...to here
    |      |            (4) following ‘false’ branch (when ‘kind != 1’)...
    |......
    |   28 |                 snprintf(buf, sizeof(buf), "%s", pfx);
    |      |                 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    |      |                 |
    |      |                 (5) ...to here
    |      |                 (6) use of uninitialized value ‘pfx’ here
    |