Should a DW_OP_implicit_value be taken from the left end?
Andreas Arnez <[email protected]>
| Newsgroups | gmane.comp.gdb.devel |
|---|---|
| Message-ID | <[email protected]> |
The following patch changed how sub-values of a DW_OP_implicit_value are extracted on big-endian platforms: https://sourceware.org/ml/gdb-patches/2011-08/msg00123.html The patch seems to assume that the placement rule is similar as for DW_OP_stack_value. I think that's wrong; DW_OP_implicit_value should always be taken from the left end. (See rationale below for an explanation.) And I'd like to know whether anyone objects. I'm in the process of preparing a patch series for fixing various problems with DWARF piece handling, and the series currently contains a patch for reverting the above patch's effect on DW_OP_implicit_value. Rationale: Since DW_OP_implicit_value can express arbitrary amounts of structured or unstructured data, the notion of a "least significant byte" is meaningless. The patch above makes it impossible for a DW_OP_implicit_pointer operation to refer to any sub-value within a DW_OP_implicit_value on big-endian targets. E.g., consider this code snippet: const char foo[] = "Hello, world!"; char *a = &foo[0]; char *b = &foo[7]; IMHO the compiler should be able to describe `foo' with a single DW_OP_implicit_value operation and `a' and `b' as DW_OP_implicit_pointer operations pointing into that value. Any objections? -- Andreas