MSVC 9.0 warning in xapian-core/common/str.h

[Peter Kelm]

MSVC 9.0 complains about line 74 in "xapian-core/common/str.h":

inline std::string str(bool value) { return std::string(1, '0' | value); }

with the (bogus) message:

"warning C4806: '|' : unsafe operation: no value of type 'bool' promoted to type 'char' can equal the given constant"

Proposed resolution is to convert "value" to a "char" via static_cast:

inline std::string str(bool value) { return std::string(1, '0' | static_cast<char>(value)); }

[Olly Betts]

Thanks - committed to trunk in r12763.

[Peter Kelm]

The template functions in line 41 (tostring_unsigned) and 59 (tostring) of "common/str.cc" exhibit a similar issue. In this case, however the compiler generates a warning only as there is the "specialization" for bool as above.

Same resolution proposed as above, i.e. adding a static_cast on the "value" parameter.

[Olly Betts]

Is this really the same warning as before? There's no logical operator involved in these assignments at all - not even a bitwise one!

It's also odd that the "constructor cast" on line 42 isn't enough to avoid this warning. What revision are you seeing this in?

[Peter Kelm]

Version is svn trunk 12765.

These are the output messages from the compiler (MSVC 9.0):

.\str.cc(59) : warning C4244: 'argument' : conversion from 'long' to 'char', possible loss of data
        .\str.cc(98) : see reference to function template instantiation 'std::string tostring<long>(T)' being compiled
        with
        [
            T=long
        ]
.\str.cc(41) : warning C4244: 'argument' : conversion from 'unsigned long' to 'char', possible loss of data
        .\str.cc(104) : see reference to function template instantiation 'std::string tostring_unsigned<unsigned long>(T)' being compiled
        with
        [
            T=unsigned long
        ]
.\str.cc(59) : warning C4244: 'argument' : conversion from '__int64' to 'char', possible loss of data
        .\str.cc(110) : see reference to function template instantiation 'std::string tostring<__int64>(T)' being compiled
        with
        [
            T=__int64
        ]
.\str.cc(41) : warning C4244: 'argument' : conversion from 'unsigned __int64' to 'char', possible loss of data
        .\str.cc(116) : see reference to function template instantiation 'std::string tostring_unsigned<unsigned __int64>(T)' being compiled
        with
        [
            T=unsigned __int64
        ]

What "constructor cast" in line 42 are you referring to?

[Olly Betts]

Ah, OK. It's probably better to open a new ticket for a new issue (but never mind this time). Reopening a ticket is really for cases like when a supposed fix didn't work.

r12768 added a "constructor cast" to line 41 (sorry, 42 was a typo). Oddly I didn't add one to line 59, but I'm curious if you still get a warning for line 41 after "svn up".

[Olly Betts]

Still awaiting a response to my query about r12768, and this is a compiler warning not an error, so not worth holding up 1.1.1 further for, so bumping milestone.

[Peter Kelm]

Just tried trunk-12909. I can confirm that the warning does not appear there.

[Olly Betts]

Thanks for confirming, so this was actually fixed in 1.1.1.