Updating MDRawMiscInfo to support version 5 of the MINIDUMP_MISC_INFO_N structure.

Updating MDRawMiscInfo to support version 5 of the MINIDUMP_MISC_INFO_N structure.

The routines used to read from the structure were also modified to
accomodate for unknown future versions by skipping over the unsupported
part instead of failing.

[gsvelto, 2016-06-30 08:38:56]

gsvelto@mozilla.com changed reviewers:
+ ted mielczarek@gmail.com

[gsvelto, 2016-06-30 08:38:57]

This patch updates the MDRawMiscInfo structure to include the fields from
version 5 of the MINIDUMP_MISC_INFO_N structure in the most recent Windows 10
SDK. I've updated the relevant code to properly read and print out this
structure and I've also added an extra enum with the flags used to interpret its
contents.

Additionally I've changed the code used for reading the structure so that if it
finds a bigger structure than the current supported one it will just skip over
the unknown part; this should make us resilient to further changes from
Microsoft. Note that this code kicks in only if the structure in the file is
strictly larger than the largest one we support. Other unknown sizes are
rejected straight away since we don't want to risk dealing with incomplete or
corrupted minidumps.

The patch is relatively clean save for the MD_MISCINFO5_SIZE constant definition
which contains a small hack. Version 5 of the structure has a size that is not a
multiple of 8 bytes yet it contains 8-byte wide fields. This causes most
compilers to round the structure size up by 4 bytes making its size as returned
from sizeof() larger than the on-disk structure. I've worked around this issue
by computing the size as the offset of the last field plus its size. It's not
pretty, but it's not ugly either and it should work everywhere (while things
like #pragma pack() or __attribute__((packed)) won't).

[Ted Mielczarek, 2016-08-19 17:26:03]

LGTM. It would be nice to have some tests for the "larger than the largest known
misc info struct" case, but we don't have any existing tests for the misc info
reading, so I won't pin that on you.