c++/2372: const struct parameter causes incorrect code with -O2.

c++/2372: const struct parameter causes incorrect code with -O2.

[suckfish]

>Number:         2372
>Category:       c++
>Synopsis:       const struct parameter causes incorrect code with -O2.
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    unassigned
>State:          open
>Class:          wrong-code
>Submitter-Id:   net
>Arrival-Date:   Fri Mar 23 20:26:01 PST 2001
>Closed-Date:
>Last-Modified:
>Originator:     suckfish@ihug.co.nz
>Release:        2001-03-20 snapshot.
>Organization:
>Environment:
Linux i686.
>Description:
The function "miscompiled" in the attached file is not
compiled correctly with -O2 -march=i686.

By inspecting the assembler output for the function "miscompiled", one can see that a temporary stack variable is loaded without being set. 

I discovered this in code using std::make_pair. The current prototype (with __GLIBCPP_RESOLVE_LIB_DEFECTS) has extraneous "const" decorations. Removing those would stop the use std::make_pair from triggering this bug. 
>How-To-Repeat:
Compile attached file on Linux with -O2 -march=i686.

Confirm bug by running program or visually inspecting assembler. 

Running the program prints "***Buggy***".  It should
print "OK".
>Fix:

>Release-Note:
>Audit-Trail:
>Unformatted:
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