Experimental Physics and
Industrial Control System

Dirk Zimoch via Core-talk <core-talk at aps.anl.gov> · Fri, 27 Aug 2021 09:31:46 -0000

Public bug reported:

There are multiple bugs in dbRecordNameValidate()
(modules/database/src/ioc/dbStatic/dbLexRoutines.c).

/* any character restrictions */
char c = *pos;
[...]
if(c < ' ') {
  errlogPrintf("Warning: Record/Alias name '%s' should not contain non-printable 0x%02u\n",
                         name, (unsigned)c);
}

1. The check for non-printable characters: if(c < ' ') does not consider implementations where char is signed. Characters with the high bit set are considered negative and thus <' '.
2. Printing the character with "0x%02u" prints a decimal number prefixed with 0x which is confusing (not to say wrong).
3. Casting a signed char to unsigned effectively first sign extends the char to int, then re-interprets it as unsigned int, turning a char >0x80 into a number >4294967168.
On an implementation where char is unsigned, the whole casting is pointless anyway.

This results in confusing warnings like:
Warning: Record/Alias name 'Ä' should not contain non-printable 0x4294967235

The function should explicitly use unsigned char c to fix (c < ' '), use
"0x%02x" to format c and not cast c.

** Affects: epics-base
     Importance: Undecided
         Status: New

** Patch added: "dbLexRoutines.patch"
   https://bugs.launchpad.net/bugs/1941875/+attachment/5521157/+files/dbLexRoutines.patch

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https://bugs.launchpad.net/bugs/1941875

Title:
  Buggy warning message "Record/Alias name '...' should not contain non-
  printable ...

Status in EPICS Base:
  New

Bug description:
  There are multiple bugs in dbRecordNameValidate()
  (modules/database/src/ioc/dbStatic/dbLexRoutines.c).

  /* any character restrictions */
  char c = *pos;
  [...]
  if(c < ' ') {
    errlogPrintf("Warning: Record/Alias name '%s' should not contain non-printable 0x%02u\n",
                           name, (unsigned)c);
  }

  1. The check for non-printable characters: if(c < ' ') does not consider implementations where char is signed. Characters with the high bit set are considered negative and thus <' '.
  2. Printing the character with "0x%02u" prints a decimal number prefixed with 0x which is confusing (not to say wrong).
  3. Casting a signed char to unsigned effectively first sign extends the char to int, then re-interprets it as unsigned int, turning a char >0x80 into a number >4294967168.
  On an implementation where char is unsigned, the whole casting is pointless anyway.

  This results in confusing warnings like:
  Warning: Record/Alias name 'Ä' should not contain non-printable 0x4294967235

  The function should explicitly use unsigned char c to fix (c < ' '),
  use "0x%02x" to format c and not cast c.

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Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System