i#1847 fix test fuzz_buffer failure with option -fuzz_replace_buffer

Commit log for first patchset:
---------------
i#1847 fix test fuzz_buffer failure with option -fuzz_replace_buffer

- replace mutation_start field in fuzz_state_t with MUTATION_START macro
- update load_fuzz_input() to only increase the buffer size for -fuzz_replace_buffer
- add fuzz_buffer.replace_buffer test
- shrink corpus.2.dat to test how buffe size changes on smaller corpus files

Fixes #1847
---------------

[bruening, 2016-01-18 22:08:56]

On 2016/01/18 05:52:43, zhaoqin wrote:
> - shrink corpus.2.dat to test how buffe size changes on smaller corpus files

error: "buffe"

[zhaoqin, 2016-01-18 23:29:22]

Commit log for latest patchset:
---------------
i#1847 fix test fuzz_buffer failure with option -fuzz_replace_buffer

- replace mutation_start field in fuzz_state_t with MUTATION_START macro
- update load_fuzz_input() to only increase the buffer size for
-fuzz_replace_buffer
- add fuzz_buffer.replace_buffer test
- shrink corpus.2.dat to test how buffle size changes on smaller corpus files

Fixes #1847

Review-URL: https://codereview.appspot.com/287810043
---------------

[bruening, 2016-01-19 18:11:56]

On 2016/01/18 23:29:22, zhaoqin wrote:
> - shrink corpus.2.dat to test how buffle size changes on smaller corpus files

"buffle"?

[zhaoqin, 2016-01-19 18:51:29]

Commit log for latest patchset:
---------------
i#1847 fix test fuzz_buffer failure with option -fuzz_replace_buffer

- replace mutation_start field in fuzz_state_t with MUTATION_START macro
- update load_fuzz_input() to only increase the buffer size for
-fuzz_replace_buffer
- add fuzz_buffer.replace_buffer test
- shrink corpus.2.dat to test how buffer size changes on smaller corpus files

Fixes #1847

Review-URL: https://codereview.appspot.com/287810043
---------------

[bruening, 2016-01-19 21:21:03]

LGTM w/ comments

https://codereview.appspot.com/287810043/diff/40001/drmemory/fuzzer.c
File drmemory/fuzzer.c (right):

https://codereview.appspot.com/287810043/diff/40001/drmemory/fuzzer.c#newcode661
drmemory/fuzzer.c:661: /* We only reallocate larger buffer to support the case
of using
I don't understand the comment: this CL is changing this if() here to only
reallocate a buffer that is *smaller* than the input file, not larger.  So why
do you say "We only reallocate larger"?  And what does the size have to do with
multiple mutators?

Update: reading below and the commit message, now I understand.  The grammar
errors here make it hard to understand.  Please improve this comment.

https://codereview.appspot.com/287810043/diff/40001/drmemory/fuzzer.c#newcode...
drmemory/fuzzer.c:1448: * current buffer can be used for any mutator we have
seen,
the current

https://codereview.appspot.com/287810043/diff/40001/drmemory/fuzzer.c#newcode...
drmemory/fuzzer.c:1448: * current buffer can be used for any mutator we have
seen,
s/,/./

https://codereview.appspot.com/287810043/diff/40001/drmemory/fuzzer.c#newcode...
drmemory/fuzzer.c:1449: * Xref load_fuzz_input() for when buffer is replaced.
the buffer

[bruening, 2016-01-19 21:21:25]

On 2016/01/19 18:51:29, zhaoqin wrote:
> Commit log for latest patchset:
> ---------------
> i#1847 fix test fuzz_buffer failure with option -fuzz_replace_buffer

nit: missing :

[zhaoqin, 2016-01-20 03:15:42]

Commit log for latest patchset:
---------------
i#1847: fix test fuzz_buffer failure with option -fuzz_replace_buffer

- replace mutation_start field in fuzz_state_t with MUTATION_START macro
- update load_fuzz_input() to only increase the buffer size for
-fuzz_replace_buffer
- add fuzz_buffer.replace_buffer test
- shrink corpus.2.dat to test how buffer size changes on smaller corpus files

Fixes #1847

Review-URL: https://codereview.appspot.com/287810043
---------------

[zhaoqin, 2016-01-20 05:21:04]

Committed as
https://github.com/DynamoRIO/drmemory/commit/ba3914cb7b08552b96d722ccc2798d4c...

Final commit log: 
---------------
i#1847: fix test fuzz_buffer failure with option -fuzz_replace_buffer

- replace mutation_start field in fuzz_state_t with MUTATION_START macro
- update load_fuzz_input() to only increase the buffer size for
-fuzz_replace_buffer
- add fuzz_buffer.replace_buffer test
- shrink corpus.2.dat to test how buffer size changes on smaller corpus files

Fixes #1847

Review-URL: https://codereview.appspot.com/287810043
---------------