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digitalmars.D.bugs - [Issue 3454] New: Inconsistent flag setting in GC.realloc()

reply d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=3454

           Summary: Inconsistent flag setting in GC.realloc()
           Product: D
           Version: 2.035
          Platform: Other
        OS/Version: Windows
            Status: NEW
          Severity: normal
          Priority: P2
         Component: druntime
        AssignedTo: sean invisibleduck.org
        ReportedBy: dsimcha yahoo.com


--- Comment #0 from David Simcha <dsimcha yahoo.com> 2009-10-29 17:26:42 PDT ---
GC.realloc() doesn't set the flags on either the old or new memory block for a
whole bunch of code paths.  I was tipped off to this by reading the code while
trying to add precise heap scanning.  Here's a test program that demonstrates
this.

import std.stdio, core.memory;

void main() {
    doTest(1);
    writeln();
    doTest(1024 * 1024);
}

void doTest(size_t multiplier) {
    auto foo = GC.malloc(8 * multiplier);
    auto bar = GC.realloc(foo, 2 * multiplier, GC.BlkAttr.NO_SCAN);

    writeln("Old block attributes:  ", GC.getAttr(foo));
    writeln("New block attributes:  ", GC.getAttr(bar));
    writeln("Old Ptr:  ", foo, "  New Ptr:  ", bar);
}

Output:
Old block attributes:  2
New block attributes:  2
Old Ptr:  961E40  New Ptr:  961E30

Old block attributes:  0
New block attributes:  0
Old Ptr:  10C0000  New Ptr:  10C0000


This is caused by the GC returning early from the B_PAGE path, or if the new
block is almost the same size as the old block.  If I get precise heap scanning
to work, I'll include a fix for this in the patch.

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Oct 29 2009
next sibling parent d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=3454


safety0ff.bugz <safety0ff.bugz gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |safety0ff.bugz gmail.com


--- Comment #1 from safety0ff.bugz <safety0ff.bugz gmail.com> 2013-10-25
12:07:56 PDT ---
I believe your test should be:
------------------------------------------------
import std.stdio, core.memory;

void main() {
    doTest(1);
    writeln();
    doTest(1024 * 1024);
}

void doTest(size_t multiplier) {
    auto foo = GC.malloc(8 * multiplier);
    writeln("Old block attributes:  ", GC.getAttr(foo));

    auto bar = GC.realloc(foo, 2 * multiplier, GC.BlkAttr.NO_SCAN);
    writeln("New block attributes:  ", GC.getAttr(bar));
    writeln("Old Ptr:  ", foo, "  New Ptr:  ", bar);
}
-------------------------------------------------
I've put an ugly fix for this here:
https://github.com/Safety0ff/druntime/commit/14148c8184b7094243f5ab74d703027d05c6e73a

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Oct 25 2013
prev sibling next sibling parent d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=3454


safety0ff.bugz <safety0ff.bugz gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |pull


--- Comment #2 from safety0ff.bugz <safety0ff.bugz gmail.com> 2013-10-27
17:01:37 PDT ---
https://github.com/D-Programming-Language/druntime/pull/645

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Oct 27 2013
prev sibling parent d-bugmail puremagic.com writes:
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--- Comment #3 from github-bugzilla puremagic.com 2013-10-31 10:26:34 PDT ---
Commits pushed to master at https://github.com/D-Programming-Language/druntime

https://github.com/D-Programming-Language/druntime/commit/4fe17c32bcfa9140e3b52e92b27474c3b60b3f95
fix Issue 3454 - inconsistent flag setting in GC.realloc()

https://github.com/D-Programming-Language/druntime/commit/487f0a1ed1aad76d1b4ca638fd25b730fd87aa4f
regression test for Issue 3454

https://github.com/D-Programming-Language/druntime/commit/0fe338f42a1225a6041bb0f7707375cfbee7b54b
Merge pull request #645 from Safety0ff/fix3454

fix Issue 3454 - inconsistent flag setting in GC.realloc()

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Oct 31 2013