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| ID | Project | Category | View Status | Date Submitted | Last Update | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 0000047 | mercury | Bug | public | 2008-02-25 11:43 | 2008-02-25 13:29 | ||||||||
| Reporter | user57 | ||||||||||||
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| Priority | normal | Severity | minor | Reproducibility | always | ||||||||
| Status | new | Resolution | open | ||||||||||
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| Target Version | Fixed in Version | ||||||||||||
| Summary | 0000047: mutable dependency problem | ||||||||||||
| Description | The program (attached) contains two mutables `a' and `b' whose initialisation mutually depends on each other. Thus to initialise `a' we need the value of `b' and vice versa. Mercury does not detect this problem, and happily compiles the program, which (unsurprisingly) seg. faults when you try and run it. Note that non-mutual dependencies may also be a problem, depending on the order the mutables are initialised. This is how the bug was discovered. | ||||||||||||
| Tags | No tags attached. | ||||||||||||
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juliensf (administrator) 2008-02-25 13:29 |
In *this* case it could be detected, but in general it is not possible to detect this at compile-time. The order in which mutables are initialised is specified in the reference manual, for initialisations within a module it is: For the purposes of determining when mutables are assigned their initial values, the expression `initial_value' behaves as though it were a predicate specified in an `initialise' directive. There is no initialisation order assumed beteween (sub-)modules. As a matter of practice I recommend that mutable initialisation expressions should not call mutable access predicates (I will add this to the reference manual). |
| Notes |
| Issue History |
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| Date Modified | Username | Field | Change |
|---|---|---|---|
| 2008-02-25 11:43 |
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New Issue | |
| 2008-02-25 11:43 |
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File Added: crash.m | |
| 2008-02-25 13:29 | juliensf | Note Added: 0000079 | |
| Issue History |