Hello, The __builtin___clear_cache() GCC builtin is used for example by the libffi library RISC-V port to flush the I-Cache after modifying the code. On RISC-V the internal implementation of this GCC builtin assumes the C library provides a __riscv_flush_icache() function. glibc implements this function in sysdeps/unix/sysv/linux/riscv/flush-icache.c. Due to the lack of this function in uClibc-ng, building anything that links against libffi fails, for example, libglib2: FAILED: gobject/gobject-query /home/test/autobuild/run/instance-0/output-1/host/bin/riscv64-buildroot-linux-uclibc-gcc -o gobject/gobject-query gobject/gobject-query.p/gobject-query.c.o -Wl,--as-needed -Wl,--no-undefined -Wl,-O1 -Wl,--start-group glib/libglib-2.0.so.0.6400.4 gobject/libgobject-2.0.so.0.6400.4 -Wl,--end-group -pthread '-Wl,-rpath,$ORIGIN/../glib:$ORIGIN/' -Wl,-rpath-link,/home/test/autobuild/run/instance-0/output-1/build/libglib2-2.64.4/build/glib -Wl,-rpath-link,/home/test/autobuild/run/instance-0/output-1/build/libglib2-2.64.4/build/gobject /home/test/autobuild/run/instance-0/output-1/host/lib/gcc/riscv64-buildroot-linux-uclibc/9.3.0/../../../../riscv64-buildroot-linux-uclibc/bin/ld: /home/test/autobuild/run/instance-0/output-1/host/riscv64-buildroot-linux-uclibc/sysroot/usr/lib64/libffi.so.7: undefined reference to `__riscv_flush_icache' collect2: error: ld returned 1 exit status Would it be possible to implement this function in uClibc-ng ? Best regards, Thomas Petazzoni -- Thomas Petazzoni, CTO, Bootlin Embedded Linux and Kernel engineering https://bootlin.com