STABS: Questions

Next: Stab Sections, Previous: Expanded Reference, Up: Top [Contents][Index]

## Appendix E Questions and Anomalies

- For GNU C stabs defining local and global variables (`N_LSYM` and `N_GSYM`), the desc field is supposed to contain the source line number on which the variable is defined. In reality the desc field is always 0. (This behavior is defined in `dbxout.c` and putting a line number in desc is controlled by ‘`#ifdef WINNING_GDB`’, which defaults to false). GDB supposedly uses this information if you say ‘`list var`’. In reality, var can be a variable defined in the program and GDB says ‘`function var not defined`’.
- In GNU C stabs, there seems to be no way to differentiate tag types: structures, unions, and enums (symbol descriptor ‘`T`’) and typedefs (symbol descriptor ‘`t`’) defined at file scope from types defined locally to a procedure or other more local scope. They all use the `N_LSYM` stab type. Types defined at procedure scope are emitted after the `N_RBRAC` of the preceding function and before the code of the procedure in which they are defined. This is exactly the same as types defined in the source file between the two procedure bodies. GDB over-compensates by placing all types in block #1, the block for symbols of file scope. This is true for default, ‘`-ansi`’ and ‘`-traditional`’ compiler options. (Bugs gcc/1063, gdb/1066.)
- What ends the procedure scope? Is it the proc block’s `N_RBRAC` or the next `N_FUN`? (I believe its the first.)