Avoid undefined behavior using CFlatData in CScript serialization #4293

1. 
   laanwj commented at 8:19 AM on June 5, 2014: member

   &vch[vch.size()] and even &vch[0] on vectors can cause assertion errors with VC in debug mode. This is the problem mentioned in #4239. The deeper problem with this is that we rely on undefined behavior.

   • Add begin_ptr and end_ptr functions that get the beginning and end pointer of vector in a reliable way that copes with empty vectors and doesn't reference outside the vector (see https://stackoverflow.com/questions/1339470/how-to-get-the-address-of-the-stdvector-buffer-start-most-elegantly/1339767#1339767).
   • Add a convenience constructor to CFlatData that wraps a vector.

   I added begin_ptr and end_ptr as separate functions as I imagine they will be useful in more places. @LongShao007 this was your issue, can you help test?

2. 
   LongShao007 commented at 12:23 PM on June 8, 2014: contributor

   The test is passed. I copy the files ( script.h and serialize.h ) to my VC project, modify the code, do the white testing, debug the program many times, don't cause assertion errors ( vector subscript out of range ) .

3. 
   laanwj commented at 8:45 AM on June 10, 2014: member

   Thanks for testing @LongShao007

4. laanwj added this to the milestone 0.10.0 on Jun 19, 2014
5. 
   petertodd commented at 1:33 PM on June 21, 2014: contributor

   ACK

6. 
   sipa commented at 2:11 PM on June 21, 2014: member

   Untested ACK.

7. 
   BitcoinPullTester commented at 1:41 AM on June 23, 2014: none

   Automatic sanity-testing: PASSED, see http://jenkins.bluematt.me/pull-tester/p4293_2ede43ebe0e87f982747feaec62aeefaf12c3a41/ for binaries and test log. This test script verifies pulls every time they are updated. It, however, dies sometimes and fails to test properly. If you are waiting on a test, please check timestamps to verify that the test.log is moving at http://jenkins.bluematt.me/pull-tester/current/ Contact BlueMatt on freenode if something looks broken.

8. Avoid undefined behavior using CFlatData in CScript serialization

   `&vch[vch.size()]` and even `&vch[0]` on vectors can cause assertion
   errors with VC in debug mode. This is the problem mentioned in #4239.
   The deeper problem with this is that we rely on undefined behavior.
   
   - Add `begin_ptr` and `end_ptr` functions that get the beginning and end
     pointer of vector in a reliable way that copes with empty vectors and
     doesn't reference outside the vector
   (see https://stackoverflow.com/questions/1339470/how-to-get-the-address-of-the-stdvector-buffer-start-most-elegantly/1339767#1339767).
   - Add a convenience constructor to CFlatData that wraps a vector.
   
   I added `begin_ptr` and `end_ptr` as separate functions as I imagine
   they will be useful in more places.

   fa126effc2
9. laanwj merged this on Jun 23, 2014
10. laanwj closed this on Jun 23, 2014

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11. laanwj referenced this in commit 5459116d61 on Jun 23, 2014
12. MarcoFalke locked this on Sep 8, 2021

Milestone
0.10.0