| Summary: | Pretty Printers - unable to create variable object (string value from children()) | ||
|---|---|---|---|
| Product: | gdb | Reporter: | David Docteur <david.docteur> |
| Component: | varobj | Assignee: | Tom Tromey <tromey> |
| Status: | RESOLVED FIXED | ||
| Severity: | normal | CC: | alex.zhigay, tromey, xdje42 |
| Priority: | P2 | ||
| Version: | 7.3 | ||
| Target Milestone: | 14.1 | ||
| Host: | Target: | ||
| Build: | Last reconfirmed: | ||
| Attachments: |
Unable to create variable object issue
using same name as in class attributes |
||
This is related to bug 17529. There may even be an existing bug for this (Eclipse printing value as a char array). Not sure about the MI errors though. Thanks for your answer. I just read what you wrote: "Eclipse is taking "name" and assuming it's a class member." The MI errors were due to the fact that I was using different names in my pretty printer than the ones in my class. Now, I can see the "char[N]" in the 'Type' column and the address of the object in the 'Value' column within Eclipse. Created attachment 8258 [details]
using same name as in class attributes
Any workaround for this problem? How to return string from children()? This seems to be two different bugs.
First, if children returns strings, they don't seem to appear.
I get this from my test:
^done,numchild="5",children=[child={name="tval.1",exp="1",numchild="8",value="[8]",type="char [8]"},child={name="tval.2",exp="2",numchild="7",value="[7]",type="char [7]"},child={name="tval.3",exp="3",numchild="7",value="[7]",type="char [7]"},child={name="tval.4",exp="4",numchild="7",value="[7]",type="char [7]"},child={name="tval.5",exp="5",numchild="6",value="[6]",type="char [6]"}],has_more="0"
The string values don't appear at all, instead for some reason
we're getting map "indices".
Second, the name returned by the printer doesn't necessarily
correspond to any kind of sub-object. This is the part that is
bug#17529.
This turns out to be this code in c_value_of_variable:
case TYPE_CODE_ARRAY:
return string_printf ("[%d]", var->num_children);
i.e., the weird short-circuiting thing strikes again.
I have a mildly hacky (given varobj, what else) patch for this. The master branch has been updated by Tom Tromey <tromey@sourceware.org>: https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=aa15623fe68b3151ed54a7365b5a5226b538851a commit aa15623fe68b3151ed54a7365b5a5226b538851a Author: Tom Tromey <tromey@adacore.com> Date: Thu Aug 31 13:01:00 2023 -0600 Allow pretty-printer 'children' method to return strings A user noticed that, while a pretty-printer can return Python strings from its "children" method, this does not really work for MI. I tracked this down to my_value_of_variable calling into c_value_of_variable, which specially handles arrays and structures -- not using the actual contents of the string. Now, this part of MI seems bad to me, but rather than change that, this applies the fix to only dynamic varobjs, which is the only scenario where a string like this can really be returned. Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=18282 Reviewed-by: Keith Seitz <keiths@redhat.com> Fixed. |
Created attachment 8255 [details] Unable to create variable object issue Hi guys, I am using Eclipse Kepler, GDB 7.3.1 and working on a project with pretty printers (Python 2.7). The problem is that I am trying to display a "prettyfied" object having children and the string type is displayed as characters array. Types such as int or long are displayed properly. Those children are obtained from a Python list object such as follow: class TestPrinter: "Print a test printer" def __init__(self, val): self.val = val def to_string(self): return "map" def children(self): streetno = {"1":"testing", "2":"Dravid", "3":"Sehwag", "4":"Laxman","5":"Kohli"} for field in sorted(streetno.keys()): if field is not None: yield field, str(streetno[field]) def str_lookup_function(val): lookup_tag = val.type.tag if lookup_tag == None: return None regex = re.compile("^test$") if regex.match(lookup_tag): return TestPrinter(val) If I return a simple string from to_string() (without calling the children() function) then it works well, and displayed as a string within Eclipse in the "Value" column. But in this case, the children of my object are displayed as char[]. I can expand the content of each, which displays character by character and its ASCII value. Then, once I click on the child itself I get the following error: 1 char [33] Error: Multiple errors reported.\ Failed to execute MI command: -var-create - * &((((this)->test_object)).1) Error message from debugger back end: -var-create: unable to create variable object\ Failed to execute MI command: -var-create - * &((((this)->test_object)).1) Error message from debugger back end: -var-create: unable to create variable object\ Unable to create variable object The expected behavior would be, of course, to see the full string instead of "Error: Failed to execute MI ..." Thank you very much for your help !