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Merged
merged 2 commits into from
May 5, 2020
Merged

Add documentation for memory primitives #5333

merged 2 commits into from
May 5, 2020

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danpoe
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@danpoe danpoe commented May 5, 2020 •
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  • Each commit message has a non-empty body, explaining why the change was made.
  • n/a Methods or procedures I have added are documented, following the guidelines provided in CODING_STANDARD.md.
  • n/a The feature or user visible behaviour I have added or modified has been documented in the User Guide in doc/cprover-manual/
  • n/a Regression or unit tests are included, or existing tests cover the modified code (in this case I have detailed which ones those are in the commit message).
  • n/a My commit message includes data points confirming performance improvements (if claimed).
  • My PR is restricted to a single feature or bugfix.
  • n/a White-space or formatting changes outside the feature-related changed lines are in commits of their own.

NlightNFotis
NlightNFotis approved these changes May 5, 2020
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I think it's good to go.

My only preference would be to pick either cbmc or CBMC and stick with it for all references to it for consistency's sake.

doc/architectural/memory-primitives.md
variable would correspond to an object of size 4, and memory allocated via
`malloc(10)` would correspond to an object of size 10.

A pointer then consists of two parts: the upper n bits form the object ID, and
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could this be changed to n?

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Here the n doesn't refer to code or commandline text or something like that so I think it shouldn't be highlighted that way.

@danpoe danpoe force-pushed the docs/memory-primitives branch from 9f4cac8 to ff21d95 Compare May 5, 2020 11:38
@danpoe danpoe marked this pull request as ready for review May 5, 2020 13:00
@danpoe danpoe added the aws Bugs or features of importance to AWS CBMC users label May 5, 2020
peterschrammel
peterschrammel approved these changes May 5, 2020
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doc/architectural/memory-primitives.md Outdated
\page memory-primitives Memory Primitives

This document describes the semantics and usage of memory-related and
pointer-related primitives in cbmc.
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Suggested change
pointer-related primitives in cbmc.
pointer-related primitives in CBMC.

doc/architectural/memory-primitives.md Outdated
# Background


## Memory and pointers in cbmc
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Suggested change
## Memory and pointers in cbmc
## Memory and Pointers in CBMC

doc/architectural/memory-primitives.md Outdated
## Memory and pointers in cbmc

When cbmc analyzes a program, by default it uses the architectural parameters of
the platform it is running on. That is, on a 64-bit system, cbmc will treat
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Suggested change
the platform it is running on. That is, on a 64-bit system, cbmc will treat
the platform it is running on. That is, on a 64-bit system, CBMC will treat

etc

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Done

doc/architectural/memory-primitives.md Outdated
integer values, and then constrained to negative values via the assumption.
In cbmc, like uninitialized integers, uninitialized pointers are treated as
having a nondeterministic value. That is, the value of the pointer itself is
nondeterministically chosen, though **no memory is allocated**.
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Maybe say that you are going to describe what can be expected from an intitialized pointer below.

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Added a sentence saying that pointers should be explicitely initialized

doc/architectural/memory-primitives.md
allocated memory, or is out of bounds of the memory object it points to (i.e.,
the memory object identified by `__CPROVER_POINTER_OBJECT(p)`).


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Maybe say upfront that some operations, particularly on invalid pointers, are unspecified. Say how I can detect that I have something with unspecified semantics in my harness.

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Done

@danpoe danpoe force-pushed the docs/memory-primitives branch from ff21d95 to 62a4b55 Compare May 5, 2020 13:51
@danpoe danpoe merged commit 5d4c4a8 into diffblue:develop May 5, 2020
@danpoe danpoe deleted the docs/memory-primitives branch June 2, 2020 17:06
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@NlightNFotis NlightNFotis NlightNFotis approved these changes

@peterschrammel peterschrammel peterschrammel approved these changes

@chrisr-diffblue chrisr-diffblue Awaiting requested review from chrisr-diffblue

@kroening kroening Awaiting requested review from kroening kroening is a code owner

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