Experimental Physics and
Industrial Control System

Mark Rivers via Core-talk <core-talk at aps.anl.gov> · Thu, 17 Sep 2020 01:47:15 +0000

The warning is this:

[epics@viper asyn]$ make -s
In function ‘setEnums.constprop’,
    inlined from ‘interruptCallbackEnumBi’ at ../../asyn/devEpics/devAsynInt32.c:759:5:
../../asyn/devEpics/devAsynInt32.c:444:25: warning: ‘strncpy’ forming offset [27, 51] is out of the bounds [0, 26] [-Warray-bounds]
         if (outStrings) strncpy(&outStrings[i*MAX_ENUM_STRING_SIZE], inStrings[i], MAX_ENUM_STRING_SIZE-1);

So the compiler thinks I am passing an array of 26 byes, and so complains that I am writing to bytes 27 to 51. But actually I know that the array I am writing to is not really just 26 bytes long, it is actually larger. How do I communicate that knowledge to the compiler?

Mark

Sent from my iPhone

On Sep 16, 2020, at 8:37 PM, Chris Johns <chrisj at rtems.org> wrote:

On 17/9/20 11:28 am, Mark Rivers wrote:
That article is interesting but is about string truncation.  The warnings I am worried about are actually incorrectly flagging buffer overflow. I am hoping there is a cast or other method to avoid them.

OK, I am not across the full context. Reviewing the suggested patch the post
hinted that GCC looks for the terminating nul being written:

if (outStrings) {
strncpy(&outStrings[i*MAX_ENUM_STRING_SIZE], inStrings[i], MAX_ENUM_STRING_SIZE);
outStrings[i*MAX_ENUM_STRING_SIZE + MAX_ENUM_STRING_SIZE-1] = '\0';
}

New string functions in base don’t really help me since asyn needs to build, preferably without such warnings, on older versions of base.

That makes things harder.

Chris

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System