werat added a comment.
In D98370#2705741 <https://reviews.llvm.org/D98370#2705741>, @jingham wrote:
> Sure. But but when I was poking around at it a little bit, it seems like the
> other use cases already work, and the only one that was failing was the case
> where you call persist on a persistent variable. If that is really true,
> then maybe we should fix the failing case directly.
Right now `Persist()` doesn't really work for values created via
`CreateValueFromData`. You can read them, but can't modify:
>>> data = lldb.SBData.CreateDataFromUInt64Array(lldb.process.GetByteOrder(),
lldb.process.GetAddressByteSize(), [42])
>>> v = lldb.target.CreateValueFromData('v', data,
lldb.target.GetBasicType(lldb.eBasicTypeUnsignedLong))
>>> v.value
'42'
>>> vp = v.Persist()
>>> vp.name
'$3'
>>> lldb.frame.EvaluateExpression('$3').value
'42'
>>> lldb.frame.EvaluateExpression('++$3 + 1').value
>>> lldb.frame.EvaluateExpression('++$3 + 1').error.GetCString()
"error: supposed to interpret, but failed: Interpreter couldn't read from
memory\n"
However I realized my patch doesn't completely fixes it either:
>>> data = lldb.SBData.CreateDataFromUInt64Array(lldb.process.GetByteOrder(),
lldb.process.GetAddressByteSize(), [42])
>>> v = lldb.target.CreateValueFromData('v', data,
lldb.target.GetBasicType(lldb.eBasicTypeUnsignedLong))
>>> vp = v.Persist()
>>> vp.name
'$0'
>>> lldb.frame.EvaluateExpression('$0').value
'42'
>>> lldb.frame.EvaluateExpression('++$0').value
'43'
>>> lldb.frame.EvaluateExpression('++$0').value
'44'
>>> vp.value
'42'
In D98370#2705741 <https://reviews.llvm.org/D98370#2705741>, @jingham wrote:
> Not sure why? The API is a request: "I made a variable somehow, and I would
> like you to make it persist so I can use its value later on even if the
> underlying data has changed." Why do you care whether you get a copy of an
> already persistent or just a shared value?
You're right, I got confused by something else. I don't care if I get a new
name/copy, as long as I can use it by the returned name it's fine. However I
want to point out that the current API does generate a new name every time (but
the it points to the same data):
>>> x = lldb.frame.FindVariable('x')
>>> x.value
'1'
>>> xp1 = x.Persist()
>>> xp1.name
'$0'
>>> xp2 = x.Persist()
>>> xp2.name
'$1'
>>> lldb.frame.EvaluateExpression('++$0 + ++$1').value
'3'
>>> xp1.value
'3'
>>> xp2.value
'3'
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D98370/new/
https://reviews.llvm.org/D98370
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