By default, Newlib uses a huge object of type struct _reent to store
thread-specific data. This object is returned by __getreent() if the
__DYNAMIC_REENT__ Newlib configuration option is defined.
The reentrancy structure contains for example errno and the standard input,
output, and error file streams. This means that if an application only uses
errno it has a dependency on the file stream support even if it does not use
it. This is an issue for lower end targets and applications which need to
qualify the software according to safety standards (for example ECSS-E-ST-40C,
ECSS-Q-ST-80C, IEC 61508, ISO 26262, DO-178, DO-330, DO-333).
If the new _REENT_THREAD_LOCAL configuration option is enabled, then struct
_reent is replaced by dedicated thread-local objects for each struct _reent
member. The thread-local objects are defined in translation units which use
the corresponding object.
A few files were missing headers for memset/malloc, likely missed
because the files don't directly call the functions, rather they
come in via macros in libc/include/sys/reent.h:
#define _REENT_CHECK(var, what, type, size, init) do { \
struct _reent *_r = (var); \
if (_r->what == NULL) { \
_r->what = (type)malloc(size); \
#define _REENT_CHECK_ASCTIME_BUF(var) \
_REENT_CHECK(var, _asctime_buf, char *, _REENT_ASCTIME_SIZE, \
memset((var)->_asctime_buf, 0, _REENT_ASCTIME_SIZE))
Without these fixes, implicit function signatures are provided,
which gcc warns could cause aliasing issues down the line:
../../../../../../../newlib-2.5.0/newlib/libc/time/asctime.c:62:3: warning: type of 'memset' does not match original declaration [-Wlto-type-mismatch]
/Volumes/code/external/newlib-cygwin/newlib/libc/include/string.h:29:7: note: return value type mismatch
_PTR _EXFUN(memset,(_PTR, int, size_t));
^
/Volumes/code/external/newlib-cygwin/newlib/libc/include/string.h:29:7: note: 'memset' was previously declared here
/Volumes/code/external/newlib-cygwin/newlib/libc/include/string.h:29:7: note: code may be misoptimized unless -fno-strict-aliasing is used
../../../../../../../newlib-2.5.0/newlib/libc/time/asctime.c:62:3: warning: type of 'malloc' does not match original declaration [-Wlto-type-mismatch]
/Volumes/code/external/newlib-cygwin/newlib/libc/include/malloc.h:37:13: note: return value type mismatch
extern _PTR malloc _PARAMS ((size_t));
^
/Volumes/code/external/newlib-cygwin/newlib/libc/include/malloc.h:37:13: note: 'malloc' was previously declared here
/Volumes/code/external/newlib-cygwin/newlib/libc/include/malloc.h:37:13: note: code may be misoptimized unless -fno-strict-aliasing is used
../../../../../../../newlib-2.5.0/newlib/libc/time/lcltime.c:58:3: warning: type of 'malloc' does not match original declaration [-Wlto-type-mismatch]
/Volumes/code/external/newlib-cygwin/newlib/libc/include/malloc.h:37:13: note: return value type mismatch
extern _PTR malloc _PARAMS ((size_t));
^
/Volumes/code/external/newlib-cygwin/newlib/libc/include/malloc.h:37:13: note: 'malloc' was previously declared here
/Volumes/code/external/newlib-cygwin/newlib/libc/include/malloc.h:37:13: note: code may be misoptimized unless -fno-strict-aliasing is used
../../../../../../../newlib-2.5.0/newlib/libc/string/strsignal.c:70:3: warning: type of 'malloc' does not match original declaration [-Wlto-type-mismatch]
/Volumes/code/external/newlib-cygwin/newlib/libc/include/malloc.h:37:13: note: return value type mismatch
extern _PTR malloc _PARAMS ((size_t));
^
/Volumes/code/external/newlib-cygwin/newlib/libc/include/malloc.h:37:13: note: 'malloc' was previously declared here
/Volumes/code/external/newlib-cygwin/newlib/libc/include/malloc.h:37:13: note: code may be misoptimized unless -fno-strict-aliasing is used
Including the proper headers elminates the implicit function
signatures and these warnings.
Matt Joyce
Yaakov Selkowitz
Pat Pannuto
Jeff Johnston
Matthew Green
Christopher Faylor