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Date: Tue, 8 Dec 2020 12:25:32 +0100
From: Shahab Vahedi <shahab.vahedi@gmail.com>
To: Olivia Nelson <the.warl0ck.1989@gmail.com>
Cc: gdb@sourceware.org
Subject: Re: Can't print in gdb
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You will need either to typecast:
(gdb) printf "prefix:%s\n", (char *) substr

Or use the member variable:
(gdb) printf "prefix:%s\n", substr.str


Cheers,
Shahab