39712 - Work around the /GT bug of MSVC 6.0 SP3

Status: RESOLVED FIXED

(NSPR :: NSPR, defect, P3)

Description

[Wan-Teh Chang]

It appears that the /O2 /GT flag of MSVC 6.0 SP3
fails to generate fiber-safe code to access
static thread-local storage, and there are
ways to work around this compiler optimization
bug.  We need to confirm this bug with Microsoft.

Comment 1

[Wan-Teh Chang]

Attachment: Bug report submitted to Microsoft.

Comment 2

[Wan-Teh Chang]

Attachment: Sample code that demonstrates the problem.

Comment 3

[Wan-Teh Chang]

Attachment: Proposed workaround.

Comment 4

[Wan-Teh Chang]

Still awaiting a response from Microsoft.

Checked in the workaround (attachment id=8868) on
the main trunk.
/cvsroot/mozilla/nsprpub/config/WIN32.mk, revision 3.10
/cvsroot/mozilla/nsprpub/pr/src/md/windows/ntthread.c, revision 3.10

This workaround needs to be thoroughly tested.

Comment 5

[Wan-Teh Chang]

This compiler bug may be fixed in MSVC 6.0 SP4:
Q262515: The /GT compiler option leaves TLSIndex as a constant.
The URL for that Knowledge Base article is
http://support.microsoft.com/support/kb/articles/q262/5/15.asp.

Larry will test SP4 to see if it fixes this bug.

Comment 6

[Wan-Teh Chang]

Attachment: Disassembly of function Switch() in sample code fiber.c under MSVC 6.0 SP4.

Comment 7

[Wan-Teh Chang]

I verified that MSVC 6.0 SP4 generated correct code for
the Switch() function in the sample code fiber.c.  (See
attachment id=10721.)

Larry verified that NSPR's cvar2 test does not hang on
a dual-CPU Windows NT machine when NSPR is built optimized
with MSVC 6.0 SP4.  (That test hangs on a dual-CPU box
if NSPR is built optimized with MSVC 6.0 SP3.)

So I removed the workaround for this compiler bug in
ntthread.c.
/cvsroot/mozilla/nsprpub/pr/src/md/windows/ntthread.c, revision 3.13

We will require MSVC 6.0 SP4 for building the Windows NT
version of NSPR. MSVC 6.0 SP4 can be downloaded from
http://msdn.microsoft.com/vstudio/sp.

Marked the bug fixed.

Comment 8

[Wan-Teh Chang]

I removed the -Og- workaround for this bug in WIN32.mk on
the NSPRPUB_RELEASE_4_0_BRANCH.
/cvsroot/mozilla/nsprpub/config/WIN32.mk, revision 3.9.18.1

On the NSPRPUB_CLIENT_BRANCH.
/cvsroot/mozilla/nsprpub/config/WIN32.mk, revision 3.9.32.1