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IDProjectCategoryView StatusDate SubmittedLast Update
0002353Frama-CPlug-in > wppublic2018-02-01 13:272019-10-17 18:01
Assigned Tocorrenson 
StatusclosedResolutionno change required 
PlatformSulfur-20171101OSOS VersionUbuntu 17.04
Product VersionFrama-C 16-Sulfur 
Target VersionFixed in Version 
Summary0002353: alt-ergo goals generated directly / via why3 differ in provability
DescriptionI generated an Alt-Ergo proof obligation for the ensures clause "xxx" (line 1140) of the attached program "search_n_standalone.c" (which was obtained from "search_n" in "Acsl by example" by "gcc -E -C"). When I did this directly (see attached script "fd"), it was proven without problems. However, when I did this via Why3 (see script "fw"), Alt-Ergo responded "Don't know" after 0.1 seconds. In order to compare both mlw files given to Alt-Ergo, I moved the goal of the via-Why3 file into the direct file; it became provable there. Removing as many axioms and definitions as possible while keeping the (non-)provability, I obtained the files "xxx_direct.mlw" and "xxx_via_why3.mlw". It seems that the former defines and uses "shift_sint32", while the latter does not (it uses "shift" instead). Probably, this is the reason for the different outcomes of Alt-Ergo. Although the observed issue may not be bug (both mlw files may be semanically equivalent), it might be desirable to unify the proof obligations given to Alt-Ergo on different pathways.
TagsNo tags attached.
Attached Filesc file icon search_n_standalone.c [^] (35,513 bytes) 2018-02-01 13:27 [Show Content]
? file icon fd [^] (382 bytes) 2018-02-01 13:27 [Show Content]
? file icon fw [^] (602 bytes) 2018-02-01 13:28 [Show Content]
? file icon xxx_direct.mlw [^] (3,871 bytes) 2018-02-01 13:28
? file icon xxx_via_why3.mlw [^] (3,589 bytes) 2018-02-01 13:28

- Relationships

-  Notes
Jochen (reporter)
2018-02-01 13:31

I changed some layout and capitalization in the mlw files to reduce their differences found by "diff"; this shouldn't have affected their semantics.
correnson (manager)
2019-10-17 17:13

Actually, the wp-native output for alt-ergo differs from the why3 output for alt-ergo. The second one is now the default, and the former one will be deprecated.

- Issue History
Date Modified Username Field Change
2018-02-01 13:27 Jochen New Issue
2018-02-01 13:27 Jochen Status new => assigned
2018-02-01 13:27 Jochen Assigned To => correnson
2018-02-01 13:27 Jochen File Added: search_n_standalone.c
2018-02-01 13:27 Jochen File Added: fd
2018-02-01 13:28 Jochen File Added: fw
2018-02-01 13:28 Jochen File Added: xxx_direct.mlw
2018-02-01 13:28 Jochen File Added: xxx_via_why3.mlw
2018-02-01 13:31 Jochen Note Added: 0006516
2019-10-17 17:13 correnson Note Added: 0006904
2019-10-17 17:13 correnson Status assigned => resolved
2019-10-17 17:13 correnson Resolution open => no change required
2019-10-17 18:01 signoles Status resolved => closed

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