Github user maskit commented on the pull request:
https://github.com/apache/trafficserver/pull/542#issuecomment-203732053
@jpeach
I added some codes for debug and got these output. The rare case is
happening.
(I built with --enable-debug and ASAN using clang on OSX.)
Output:
```
mime_hdr_set_accelerators_and_presence_bits(hdr 0x61d0001ab908, field
0x6250001aba98): &(mh->m_first_fblock.m_field_slots[0]) = 0x61d0001ab958
(int)(field - &(mh->m_first_fblock.m_field_slots[0])) = 0xA
(long)(field - &(mh->m_first_fblock.m_field_slots[0])) = 0x40000000A
(ptrdiff_t)(field - &(mh->m_first_fblock.m_field_slots[0])) = 0x40000000A
mime_hdr_field_slotnum(hdr 0x61d0001ab908, field 0x6250001ab998): first =
0x61d0001ab958
(int)(field - first) = 0x2
(long)(field - first) = 0x400000002
(ptrdiff_t)(field - first) = 0x400000002
```
Debug code1:
``` c
if ((int)(field - &(mh->m_first_fblock.m_field_slots[0])) >= 0 &&
(int)(field - &(mh->m_first_fblock.m_field_slots[0])) <
MIME_FIELD_SLOTNUM_UNKNOWN && slot_num > UINT_MAX) {
fprintf(stderr, "mime_hdr_set_accelerators_and_presence_bits(hdr %p,
field %p): &(mh->m_first_fblock.m_field_slots[0]) = %p\n", mh, field,
&(mh->m_first_fblock.m_field_slots[0]));
fprintf(stderr, "(int)(field - &(mh->m_first_fblock.m_field_slots[0])) =
0x%X\n", (int)(field - &(mh->m_first_fblock.m_field_slots[0])));
fprintf(stderr, "(long)(field - &(mh->m_first_fblock.m_field_slots[0])) =
0x%lX\n", (long)(field - &(mh->m_first_fblock.m_field_slots[0])));
fprintf(stderr, "(ptrdiff_t)(field -
&(mh->m_first_fblock.m_field_slots[0])) = 0x%tX\n", (ptrdiff_t)(field -
&(mh->m_first_fblock.m_field_slots[0])));
}
```
Debug code2:
``` c
if ((int)(field - first) >= 0 && (int)(field - first) <
MIME_FIELD_BLOCK_SLOTS && block_slot > UINT_MAX) {
fprintf(stderr, "mime_hdr_field_slotnum(hdr %p, field %p): first = %p\n",
mh, field, first);
fprintf(stderr, "(int)(field - first) = 0x%X\n", (int)(field - first));
fprintf(stderr, "(long)(field - first) = 0x%lX\n", (long)(field - first));
fprintf(stderr, "(ptrdiff_t)(field - first) = 0x%tX\n", (ptrdiff_t)(field
- first));
}
```
However the problem doesn't seems to be caused by the optimization, adding
```MIMEFieldBlockImpl::contains(MIMEField*)``` is a good idea. It's readable
and reusable. I'll add it.
As for the tests, I had no idea. I came across the bug while I was testing
HPACK, which just uses a MIMEHdr heavily. It may be possible to write tests for
```MIMEFieldBlockImpl::contains(MIMEField*)```. The test would be:
1. Create a mime field
2. Add 2^32 to the pointer of the mime field
3. Pass the modified pointer to contains()
4. Check if the result is false
@zwoop
The type conversions are in the initial commit on the git repo, so I think
all versions should affect.
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