Symbol Errors (Debugging with GDB)

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### 18.7 Errors Reading Symbol Files

While reading a symbol file, GDB occasionally encounters problems, such as symbol types it does not recognize, or known bugs in compiler output. By default, GDB does not notify you of such problems, since they are relatively common and primarily of interest to people debugging compilers. If you are interested in seeing information about ill-constructed symbol tables, you can either ask GDB to print only one message about each such type of problem, no matter how many times the problem occurs; or you can ask GDB to print more messages, to see how many times the problems occur, with the `set complaints` command (see Optional Warnings and Messages).

The messages currently printed, and their meanings, include:

`inner block not inside outer block in symbol`

  The symbol information shows where symbol scopes begin and end (such as at the start of a function or a block of statements). This error indicates that an inner scope block is not fully contained in its outer scope blocks.

  GDB circumvents the problem by treating the inner block as if it had the same scope as the outer block. In the error message, symbol may be shown as “`(don't know)`” if the outer block is not a function.

`block at address out of order`

  The symbol information for symbol scope blocks should occur in order of increasing addresses. This error indicates that it does not do so.

  GDB does not circumvent this problem, and has trouble locating symbols in the source file whose symbols it is reading. (You can often determine what source file is affected by specifying `set verbose on`. See Optional Warnings and Messages.)

`bad block start address patched`

  The symbol information for a symbol scope block has a start address smaller than the address of the preceding source line. This is known to occur in the SunOS 4.1.1 (and earlier) C compiler.

  GDB circumvents the problem by treating the symbol scope block as starting on the previous source line.

`bad string table offset in symbol n`

  Symbol number n contains a pointer into the string table which is larger than the size of the string table.

  GDB circumvents the problem by considering the symbol to have the name `foo`, which may cause other problems if many symbols end up with this name.

`unknown symbol type `0xnn``

  The symbol information contains new data types that GDB does not yet know how to read. `0xnn` is the symbol type of the uncomprehended information, in hexadecimal.

  GDB circumvents the error by ignoring this symbol information. This usually allows you to debug your program, though certain symbols are not accessible. If you encounter such a problem and feel like debugging it, you can debug `gdb` with itself, breakpoint on `complain`, then go up to the function `read_dbx_symtab` and examine `*bufp` to see the symbol.

`stub type has NULL name`

  GDB could not find the full definition for a struct or class.

`const/volatile indicator missing (ok if using g++ v1.x), got…`

  The symbol information for a C`++` member function is missing some information that recent versions of the compiler should have output for it.

`info mismatch between compiler and debugger`

  GDB could not parse a type specification output by the compiler.

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