233809 - investigate /Za or /Zc:forScope compiler options to fix for loop scoping

Status: RESOLVED WORKSFORME

(Firefox Build System :: General, defect)

Description

[David Baron :dbaron: (⌚️UTC-4, no longer working on Mozilla)]

We should investigate whether the compiler options that force MSVC to use the
standard for-loop scoping rules work on compilers as old as VC6.  See:

http://msdn.microsoft.com/library/en-us/vccore/html/_core_.2f.za.2c_2f.ze.asp
http://msdn.microsoft.com/library/en-us/vccore/html/vcrefzcforscope.asp

And perhaps also the pragma if some embedder uses our code without our build system:
http://msdn.microsoft.com/library/en-us/vccelng/htm/pragm_8.asp

(This would leave the HP-UX compiler as the only one without correct for-loop
scoping, I think.)

Comment 1

[David Baron :dbaron: (⌚️UTC-4, no longer working on Mozilla)]

(See bug 233810 for options for the HP aCC compiler.)

Comment 2

[David Baron :dbaron: (⌚️UTC-4, no longer working on Mozilla)]

Unfortunately, this option doesn't seem to be supported in MSVC 6.0.

Comment 3

[David Baron :dbaron: (⌚️UTC-4, no longer working on Mozilla)]

this being /Zc:forScope.  I should try /Za, I guess...

Comment 4

[David Baron :dbaron: (⌚️UTC-4, no longer working on Mozilla)]

The compiler accepts -Za, but it gives errors in the string code...

Comment 5

[David Baron :dbaron: (⌚️UTC-4, no longer working on Mozilla)]

The options for 6.0 are:
http://msdn.microsoft.com/library/en-us/vccore98/HTML/_core_compiler_reference.asp

Comment 6

[David Baron :dbaron: (⌚️UTC-4, no longer working on Mozilla)]

Attachment: patch I tried

Comment 7

[jag (Peter Annema)]

What was the nature of the errors in the string code?

Comment 8

[David Baron :dbaron: (⌚️UTC-4, no longer working on Mozilla)]

So if VC++ 7.1 is the oldest supported compiler on the trunk, we could add the -Zc:forScope option to the VC++ command line options and stop requiring tolerance for both for loop scoping rules on the trunk.

Comment 9

[Benjamin Smedberg]

Yes please.

Comment 10

[David Baron :dbaron: (⌚️UTC-4, no longer working on Mozilla)]

Attachment: patch to test

My Windows build env is still VC6, so I'm not set up to build trunk.  If somebody could try this, and check that a for loop scoping case that doesn't compile without it does compile with it, that would be great...

Comment 11

[David Baron :dbaron: (⌚️UTC-4, no longer working on Mozilla)]

So this doesn't even seem to be a problem on VC8, but it would be nice if somebody tested this on VC7.1.  But I'll actually attach another patch that touches only CXXFLAGS.

Comment 12

[David Baron :dbaron: (⌚️UTC-4, no longer working on Mozilla)]

Attachment: patch to test

Comment 13

[David Baron :dbaron: (⌚️UTC-4, no longer working on Mozilla)]

So it's actually not a problem on 7.1 either.  The problem is on VC6, which doesn't even have this option.  And we still have trunk tinderboxes building with VC6.

Comment 14

[David Baron :dbaron: (⌚️UTC-4, no longer working on Mozilla)]

(And, for what it's worth, I no longer have a Windows build environment, nor the energy to try to set one up.  I deleted my working VC6 environment tonight in an effort to install VC7.1.  I installed it, but when it came to setting up the environment variables I couldn't figure out which environment variables had come from my setup of VC6, what was set by various installers, etc.  So I deleted them all, plus the install of VC7.1.  Windows isn't designed for installing and upgrading software.)

Comment 15

[Justin Wood (:Callek)]

David, is this still "wanted" in any sense?

Comment 16

[(not currently active) Ted Mielczarek]

If this is only a problem with VC6, then it's not, because we only support VC7.1 or newer on trunk.