Check snapshots for feature compatibility.

Check snapshots for feature compatibility.

 - Full snapshots must be written and read by VMs in the same
   mode (debug/release/product).
 - Snapshots with ICData must be written and read by VMs in same
   checked-mode state.
 - Snapshots with code must be written and read by VMs targeting the
   same architecture and ABI.

Fix use-after-free of VM isolate snapshot error message.

R=asiva@google.com

Committed: https://github.com/dart-lang/sdk/commit/1e389236438e5ce1655d1509aaa2e4a00fef10a1

[rmacnak, 2016-05-13 23:35:27]

rmacnak@google.com changed reviewers:
+ asiva@google.com

[siva, 2016-05-16 16:48:00]

LGTM .

https://chromiumcodereview.appspot.com/1975423002/diff/20001/runtime/vm/snaps...
File runtime/vm/snapshot.cc (right):

https://chromiumcodereview.appspot.com/1975423002/diff/20001/runtime/vm/snaps...
runtime/vm/snapshot.cc:759: expected_len < buffer_len ? expected_len :
buffer_len)) {
why not write this as 
if ((expected_len > buffer_len) ||
    strncmp(features, expected_features, expected_len)) {
  .....
  .....
}

https://chromiumcodereview.appspot.com/1975423002/diff/20001/runtime/vm/snaps...
File runtime/vm/snapshot.h (right):

https://chromiumcodereview.appspot.com/1975423002/diff/20001/runtime/vm/snaps...
runtime/vm/snapshot.h:1024: void WriteFeatures();
The comment is incorrect as it writes more than the version information. Why did
you choose to make it into two separate functions instead of going with one;

void WriteHeaderInfo();
void VerifyHeaderInfo();

[rmacnak, 2016-05-16 20:59:56]

https://chromiumcodereview.appspot.com/1975423002/diff/20001/runtime/vm/snaps...
File runtime/vm/snapshot.cc (right):

https://chromiumcodereview.appspot.com/1975423002/diff/20001/runtime/vm/snaps...
runtime/vm/snapshot.cc:759: expected_len < buffer_len ? expected_len :
buffer_len)) {
On 2016/05/16 16:48:00, siva wrote:
> why not write this as 
> if ((expected_len > buffer_len) ||
>     strncmp(features, expected_features, expected_len)) {
>   .....
>   .....
> }

Done.

https://chromiumcodereview.appspot.com/1975423002/diff/20001/runtime/vm/snaps...
File runtime/vm/snapshot.h (right):

https://chromiumcodereview.appspot.com/1975423002/diff/20001/runtime/vm/snaps...
runtime/vm/snapshot.h:1024: void WriteFeatures();
On 2016/05/16 16:48:00, siva wrote:
> The comment is incorrect as it writes more than the version information. Why
did
> you choose to make it into two separate functions instead of going with one;
> 
> void WriteHeaderInfo();
> void VerifyHeaderInfo();

I started out thinking the features string wouldn't be used in all snapshot
kinds, before I realized the mode factors in even without code. Merged.

[rmacnak, 2016-05-16 21:00:12]

Description was changed from

==========
Check snapshots for feature compatibility.

 - Full snapshots must be written and read by VMs in the same
   mode (debug/release/product).
 - Snapshots with ICData must be written and read by VMs in same
   checked-mode state.
 - Snapshots with code must be written and read by VMs targeting the
   same architecture and ABI.

Fix use-after-free of VM isolate snapshot error message.
==========

to

==========
Check snapshots for feature compatibility.

 - Full snapshots must be written and read by VMs in the same
   mode (debug/release/product).
 - Snapshots with ICData must be written and read by VMs in same
   checked-mode state.
 - Snapshots with code must be written and read by VMs targeting the
   same architecture and ABI.

Fix use-after-free of VM isolate snapshot error message.

R=asiva@google.com

Committed:
https://github.com/dart-lang/sdk/commit/1e389236438e5ce1655d1509aaa2e4a00fef10a1
==========

[rmacnak, 2016-05-16 21:00:14]

Committed patchset #2 (id:20001) manually as
1e389236438e5ce1655d1509aaa2e4a00fef10a1 (presubmit successful).

[rmacnak, 2016-05-16 21:00:27]

Description was changed from

==========
Check snapshots for feature compatibility.

 - Full snapshots must be written and read by VMs in the same
   mode (debug/release/product).
 - Snapshots with ICData must be written and read by VMs in same
   checked-mode state.
 - Snapshots with code must be written and read by VMs targeting the
   same architecture and ABI.

Fix use-after-free of VM isolate snapshot error message.

R=asiva@google.com

Committed:
https://github.com/dart-lang/sdk/commit/1e389236438e5ce1655d1509aaa2e4a00fef10a1
==========

to

==========
Check snapshots for feature compatibility.

 - Full snapshots must be written and read by VMs in the same
   mode (debug/release/product).
 - Snapshots with ICData must be written and read by VMs in same
   checked-mode state.
 - Snapshots with code must be written and read by VMs targeting the
   same architecture and ABI.

Fix use-after-free of VM isolate snapshot error message.

R=asiva@google.com

Committed:
https://github.com/dart-lang/sdk/commit/1e389236438e5ce1655d1509aaa2e4a00fef10a1
==========