OpenBSD-specific behavior of LLVM/clang
, the LLVM/clang compiler exhibits the
- clang comes with stack
protection enabled by default, equivalent to the
-fstack-protector-strong option on other
systems. The system will report any violation of the stack protector
cookie along with the function name via
- clang will generate PIE code
by default, allowing the system to load the resulting binary at a random
location. This behavior can be turned off by passing
-fno-pie to the compiler and
-nopie to the linker.
- The -fstrict-aliasing option
is turned off by default unless -Ofast has
- clang does not store its
version string in objects. There is no option to control this.
- The -pg flag is an alias of
- clang does not warn for
passing pointer arguments or assignment with different signedness outside
of -pedantic. This can be re-enabled with the
- The warning option
-Waddress-of-packed-member is disabled by
- Color diagnostic messages are disabled by default and can
be re-enabled with -fdiagnostics-color.
- The -fwrapv option to treat
signed integer overflows as defined is enabled by default to prevent
dangerous optimizations which could remove security critical overflow
free(3) builtins are disabled
to prevent undesirable optimizations of calls to these functions.