SYSROOTusrinclude

SYSROOTusrinclude is the include directory within a cross-compilation sysroot. A sysroot is a self-contained root filesystem used when building software for a different target architecture or environment. The usr/include subtree contains the target’s header files, such as standard C library declarations and other API definitions needed by source code during compilation. In a typical setup, the sysroot mirrors parts of the target filesystem, so the compiler can locate headers as if it were compiling for the actual device or OS.

The sysroot layout helps isolate host and target environments. By providing a dedicated SYSROOT/usr/include, cross-compilers can avoid mixing host-system headers with target headers, reducing compatibility issues. Headers inside this directory may include both standard library headers and target-specific headers, sometimes arranged in architecture-specific subdirectories under include. The presence and organization of SYSROOT/usrinclude can vary with toolchains, but the goal remains the same: supply accurate, self-contained declarations for the target.

Usage and integration are common across toolchains. Compilers such as GCC or Clang can be directed to use a sysroot via options like --sysroot=/path/to/sysroot. When set, include search paths and library lookups are interpreted relative to that sysroot, allowing code to be built in a host environment while targeting another system. Build systems may also propagate SYSROOT to compilers or explicitly add -I$SYSROOT/usr/include as needed.

Creation and maintenance of a SYSROOT/usrinclude tree are typically handled by toolchains or build systems. Common sources include a target SDK, Buildroot, OpenEmbedded, or Crosstool-NG-generated toolchains. Keeping this directory consistent with the target’s libc implementation and headers is essential for successful cross-compilation.