818391 - nsMultiplexInputStream.cpp(514) : error C2668: 'abs' : ambiguous call to overloaded function

Status: RESOLVED FIXED

(Core :: General, defect)

Description

[Philip Chee]

MVS2008SP1 on Windows7 x64:

c:/t1/hg/comm-central/mozilla/xpcom/io/nsMultiplexInputStream.cpp(514) : error C2668: 'abs' : ambiguous call to overloaded function
        C:\Program Files (x86)\Microsoft Visual Studio 9.0\VC\INCLUDE\math.h(485): could be 'long abs(long)'
        C:\Program Files (x86)\Microsoft Visual Studio 9.0\VC\INCLUDE\math.h(487): or       'doubleabs(double)'
        C:\Program Files (x86)\Microsoft Visual Studio 9.0\VC\INCLUDE\math.h(491): or       'float abs(float)'
        C:\Program Files (x86)\Microsoft Visual Studio 9.0\VC\INCLUDE\math.h(539): or       'long double abs(long double)'
        C:\Program Files (x86)\Microsoft Visual Studio 9.0\VC\INCLUDE\stdlib.h(380): or       'int abs(int)'
        while trying to match the argument list '(int64_t)'
c:/t1/hg/comm-central/mozilla/xpcom/io/nsMultiplexInputStream.cpp(522) : error C2668: 'abs' : ambiguous call to overloaded function
        C:\Program Files (x86)\Microsoft Visual Studio 9.0\VC\INCLUDE\math.h(485): could be 'long abs(long)'
        C:\Program Files (x86)\Microsoft Visual Studio 9.0\VC\INCLUDE\math.h(487): or       'doubleabs(double)'
        C:\Program Files (x86)\Microsoft Visual Studio 9.0\VC\INCLUDE\math.h(491): or       'float abs(float)'
        C:\Program Files (x86)\Microsoft Visual Studio 9.0\VC\INCLUDE\math.h(539): or       'long double abs(long double)'
        C:\Program Files (x86)\Microsoft Visual Studio 9.0\VC\INCLUDE\stdlib.h(380): or       'int abs(int)'
        while trying to match the argument list '(int64_t)'

Comment 1

[Mats Palmgren (inactive)]

Sorry I broke your build.  I'm a bit puzzled why it doesn't pick abs(long) though -
is 'long' not 64-bit?  If you add back the NS_ABS template in this file and
revert the change, does the build succeed?

Comment 2

[Mats Palmgren (inactive)]

C++11 is required to have std::abs(long long) but apparently MVS2008SP1 doesn't.
Perhaps we could add it to std namespace with something like:
#if VISUAL_VERSION <= 2008  // or whatever
namespace std {
  long long abs(long long v) { return llabs(v); }
}
#endif

Comment 3

[Robert Longson [:longsonr]]

(In reply to Mats Palmgren [:mats] from comment #1)
> Sorry I broke your build.  I'm a bit puzzled why it doesn't pick abs(long)
> though -
> is 'long' not 64-bit?  If you add back the NS_ABS template in this file and
> revert the change, does the build succeed?

With MS Visual Studio long is 32 bit (same as int) 64 bit would be long long.

Comment 4

[Mats Palmgren (inactive)]

I see, thanks.  Does the suggested std::abs(long long) overload work if you put
it in nsMultiplexInputStream.cpp?

Comment 5

[Robert Longson [:longsonr]]

Attachment: patch

This works. My compilation is still running so I don't know if it's the only place yet.

Comment 6

[Mats Palmgren (inactive)]

Thanks for investigating.  I think I still prefer the "long long" type though
(if it works), so we use the exact same signatures for all platforms.

Perhaps it's better to add it to nsAlgorithm.h even if it turns out to be just
this file, so that it will work for new code.  (I didn't remove any of the
#includes for nsAlgorithm.h in bug 817574)

Comment 7

[Robert Longson [:longsonr]]

Comment on attachment 688778 [details] [diff] [review]
patch

All the other files compile OK.

Comment 8

[Robert Longson [:longsonr]]

Attachment: or this...

Comment 9

[Mats Palmgren (inactive)]

Comment on attachment 688831 [details] [diff] [review]
or this...

Looks good to me, but I'm not a xpcom peer.

Comment 11

[Mats Palmgren (inactive)]

https://hg.mozilla.org/integration/mozilla-inbound/rev/16037c152c36

Comment 12

[Ed Morley [:emorley]]

https://hg.mozilla.org/mozilla-central/rev/16037c152c36