I stumbled upon a simple occurrence of -Werror=maybe-uninitialized:
../../gdb/opcodes/aarch64-opc.c: In function 'expand_fp_imm':
../../gdb/opcodes/aarch64-opc.c:2880:10: error: 'imm' may be used uninitialized in this function [-Werror=maybe-uninitialized]
return imm;
^~~
It is the compiler's fault, because this function always assigns to
'imm' if the necessary conditions are met, and it calls "assert (0)"
otherwise, but I thought it'd be clearer to have 'imm' explicitly set
to zero anyway.