mac pretty print gdb

Question

I'm on macOS High Sierra 10.13.6 and not able to get gdb to pretty print containers or strings. I followed the instructions here GDB 7.6 STL pretty print with gcc-4.8 and mac os 10.9 , cloned the gdb pretty printers and added the path to .gdbinit. However gdb still won't pretty print. I added the pretty printers after starting gdb to make sure they were registered

(gdb) python
>import sys
>sys.path.insert(0, '/Users/liamadams/Documents/gdb/python')
>from libstdcxx.v6.printers import register_libstdcxx_printers
>register_libstdcxx_printers (None)
>end
Traceback (most recent call last):
  File "<string>", line 4, in <module>
  File "/Users/liamadams/Documents/gdb/python/libstdcxx/v6/printers.py", line 1739, in register_libstdcxx_printers
    gdb.printing.register_pretty_printer(obj, libstdcxx_printer)
  File "/usr/local/Cellar/gdb/8.0.1/share/gdb/python/gdb/printing.py", line 152, in register_pretty_printer
    printer.name)
RuntimeError: pretty-printer already registered: libstdc++-v6

gdb is registering the pretty printers, I'm running gcc 8.2.0 and gdb 8.0.1. The pretty printer registered is c++-v6, should it be v8? I cloned this repo to get the pretty printers svn://gcc.gnu.org/svn/gcc/trunk/libstdc++-v3/python

I built my code using /usr/local/Cellar/gcc/8.2.0/bin/g++-8 -static-libstdc++ -g -o a.out bo co -pthread

Here is the gdb output when trying to print a string

(gdb) p currentItem
$1 = {static npos = <optimized out>, 
  _M_dataplus = {<allocator<char>> = {<new_allocator<char>> = {<No data fields>}, <No data fields>}, _M_p = 0x7ffeefbff900 "mining"}, _M_string_length = 6, {
    _M_local_buf = "mining\000\000\v\000\000\000\000\000\000", 
    _M_allocated_capacity = 113723912907117}}

(gdb) whatis currentItem
type = string

Answer 1

It seems to be a bug. A hack solution is provided in this Stack Overflow question:

Bug in gdb libstdc++ pretty-printers with gcc 8 installed from macports (macOS)

Copying from that question, you need to modify the pretty-printer code:

--- python/libstdcxx/v6/printers.py.old 2018-10-13 13:57:11.000000000 +0300
+++ python/libstdcxx/v6/printers.py 2018-10-13 14:35:55.000000000 +0300
@@ -1306,2 +1306,4 @@
     def add(self, name, function):
+        if (name.startswith('std::')):
+            self.add(name[5:], function)
         # A small sanity check.

Answer 2

Try compiling with -gdwarf-3 instead of simply -g . According to https://gcc.gnu.org/onlinedocs/gcc/Debugging-Options.html , GCC defaults to DWARF version 2 on macOS, and explicitely switching to DWARF version 3 makes the symbols correctly appear in the std:: namespace (I don't yet understand why). So you would not need to patch the pretty printers as Yongwei Wu suggests.