esp8266/tools/sdk/lib/README.md

Updating SDK libraries

After updating SDK libraries to a new version, do the following changes.

1. Remove mem_manager.o from libmain.a to use custom heap implementation

   xtensa-lx106-elf-ar -d libmain.a mem_manager.o
   

Updating libstdc++

After building gcc using crosstool-NG, get compiled libstdc++ and remove some objects:

xtensa-lx106-elf-ar d libstdc++.a pure.o
xtensa-lx106-elf-ar d libstdc++.a vterminate.o
xtensa-lx106-elf-ar d libstdc++.a guard.o
xtensa-lx106-elf-ar d libstdc++.a functexcept.o
xtensa-lx106-elf-ar d libstdc++.a del_op.o
xtensa-lx106-elf-ar d libstdc++.a del_opv.o
xtensa-lx106-elf-ar d libstdc++.a new_op.o
xtensa-lx106-elf-ar d libstdc++.a new_opv.o