musl/src/exit/assert.c, branch v1.2.0 musl - an implementation of the standard library for Linux-based systems restore _Noreturn to __assert_fail 2016-08-30T20:39:54+00:00 Rich Felker dalias@aerifal.cx 2016-08-30T20:39:54+00:00 e738b8cbe64b6dd3ed9f47b6d4cd7eb2c422b38d this reverts commit 2c1f8fd5da3306fd7c8a2267467e44eb61f12dd4. without the _Noreturn attribute, the compiler cannot use asserts to perform reachability/range analysis. this leads to missed optimizations and spurious warnings. the original backtrace problem that prompted the removal of _Noreturn was not clearly documented at the time, but it seems to happen only when libc was built without -g, which also breaks many other backtracing cases. 
this reverts commit 2c1f8fd5da3306fd7c8a2267467e44eb61f12dd4. without
the _Noreturn attribute, the compiler cannot use asserts to perform
reachability/range analysis. this leads to missed optimizations and
spurious warnings.

the original backtrace problem that prompted the removal of _Noreturn
was not clearly documented at the time, but it seems to happen only
when libc was built without -g, which also breaks many other
backtracing cases.
__assert_fail(): remove _Noreturn, to get proper stacktraces 2013-01-04T19:36:34+00:00 rofl0r retnyg@gmx.net 2013-01-01T06:59:11+00:00 2c1f8fd5da3306fd7c8a2267467e44eb61f12dd4 for _Noreturn functions, gcc generates code that trashes the stack frame, and so it makes it impossible to inspect the causes of an assert error in gdb. abort() is not affected (i have not yet investigated why). 
for _Noreturn functions, gcc generates code that trashes the
stack frame, and so it makes it impossible to inspect the causes
of an assert error in gdb.

abort() is not affected (i have not yet investigated why).
further use of _Noreturn, for non-plain-C functions 2012-09-07T03:34:10+00:00 Rich Felker dalias@aerifal.cx 2012-09-07T03:34:10+00:00 0c05bd3a9c165cf2f0b9d6fa23a1f96532ddcdb3 note that POSIX does not specify these functions as _Noreturn, because POSIX is aligned with C99, not the new C11 standard. when POSIX is eventually updated to C11, it will almost surely give these functions the _Noreturn attribute. for now, the actual _Noreturn keyword is not used anyway when compiling with a c99 compiler, which is what POSIX requires; the GCC __attribute__ is used instead if it's available, however. in a few places, I've added infinite for loops at the end of _Noreturn functions to silence compiler warnings. presumably __buildin_unreachable could achieve the same thing, but it would only work on newer GCCs and would not be portable. the loops should have near-zero code size cost anyway. like the previous _Noreturn commit, this one is based on patches contributed by philomath. 
note that POSIX does not specify these functions as _Noreturn, because
POSIX is aligned with C99, not the new C11 standard. when POSIX is
eventually updated to C11, it will almost surely give these functions
the _Noreturn attribute. for now, the actual _Noreturn keyword is not
used anyway when compiling with a c99 compiler, which is what POSIX
requires; the GCC __attribute__ is used instead if it's available,
however.

in a few places, I've added infinite for loops at the end of _Noreturn
functions to silence compiler warnings. presumably
__buildin_unreachable could achieve the same thing, but it would only
work on newer GCCs and would not be portable. the loops should have
near-zero code size cost anyway.

like the previous _Noreturn commit, this one is based on patches
contributed by philomath.
initial check-in, version 0.5.0 2011-02-12T05:22:29+00:00 Rich Felker dalias@aerifal.cx 2011-02-12T05:22:29+00:00 0b44a0315b47dd8eced9f3b7f31580cf14bbfc01