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Re: Documentation reentrancy


I send this message again, because it has been refused due to html formatting problems.

So far so good. But how do I (in a clean way) get rid off the newlib- provided __getreent() in getreent.c (libc.a)?
Any tips about how to integrate newlib with an rtos would be welcome. I want to use nilsen elektronik rtos. Do I make the newlib syscalls separately, should I put them in the newlib source tree or should I put them in the rtos source tree?
What does libgloss mean?


Cheers

Carl.
This is the error I get about getreent():
/sw/bin/m6811-elf-gcc -g -Os -mshort -I../nilsen-proc -save-temps - Wl,-m,m68hc11elf -nostdlib -L ../nilsen-proc -L /usr/local/m6811-elf/ lib/mshort -L /usr/local/m6811-elf/lib/ldscripts -L ../newlib -L /sw/ share/m6811/lib/gcc-lib/m6811-elf/3.0.4/mshort -o trein1.elf ../ nilsen-proc/start.o trein1.o -lc -lnewlib-nilsen-proc-syscalls - lnilsen-proc -lgcc
../newlib/libnewlib-nilsen-proc-syscalls.a(syscalls.o): In function `__getreent':
syscalls.i:(.text+0x14d): multiple definition of `__getreent'
/usr/local/m6811-elf/lib/mshort/libc.a(getreent.o):../../../../../../ newlib-1.14.0/newlib/libc/reent/getreent.c:8: first defined here
/sw/bin/../share/m6811/lib/gcc-lib/m6811-elf/3.0.4/../../../../m6811- elf/bin/ld: Disabling relaxation: it will not work with multiple definitions
collect2: ld returned 1 exit status
make: *** [trein1.elf] Error 1



Op 1-mrt-2006, om 0:27 heeft Jeff Johnston het volgende geschreven:


The __DYNAMIC_REENT__ flag is currently set manually in libc/ include/sys/config.h. It is looked at by libc/include/sys/reent.h which then defines _REENT to be a call to __getreent() instead of the default which is to define _REENT to be _impure_ptr.

The libgloss reference was for you to look at a working libgloss implementation to figure out how to write a libgloss library. It has nothing to do with your reentrancy problem.

-- Jeff J.

It is not documented

Carl Denzen Van wrote:
Hello Jeff,
I cannot figure out how to "Set the __DYNAMIC_REENT__ flag for the platform" (and I think you named it also "__DYNAMIC_REENTRANCY__"). Where can I find documentation?
Do I have to call the _getreent() myself in the stubs? Or is it already implemented at another level in newlib?
In the working libgloss/mn10300 I did not find anything about reentrancy in the way you explained.
Carl.
Op 16-feb-2006, om 0:21 heeft Jeff Johnston het volgende geschreven:
Carl Denzen Van wrote:

Thank you. I will implement choice 4.



And meanwhile I ran into the next errors when I compile the simple stubs from the docs:


I wouldn't suggest implementing those strictly from the docs as they have the wrong names to start with and there is already an implemented library of these stubs available for you in libgloss/ libnosys (sans _exit and crt0 which you should provide in assembler). You simply add -lnosys to the end of your link or embed the reference in your ld script or spec file.

I usually suggest looking at working implementations (e.g. libgloss/ mn10300).

-- Jeff J.



stubsc.c: In function `sbrk':
stubsc.c:108: `stack_ptr' undeclared (first use in this function)
stubsc.c:108: (Each undeclared identifier is reported only once
stubsc.c:108: for each function it appears in.)
stubsc.c:110: warning: implicit declaration of function `_write'
stubsc.c: At top level:
stubsc.c:122: conflicting types for `stat'
/usr/local/m6811-elf/include/sys/stat.h:124: previous declaration of `stat'
stubsc.c:131: warning: `struct tms' declared inside parameter list
stubsc.c:131: warning: its scope is only this definition or declaration, which is probably not what you want.
stubsc.c: In function `write':
stubsc.c:162: warning: implicit declaration of function `writechar'
Another improvement to the documentation would be to mention the files to be included. I include (after "grep"ping an evening for the missing entries):
#include <sys/types.h>
#include <sys/stat.h>
#include <stdlib.h>
#include <errno.h>
#undef errno
extern int errno;
Carl van Denzen. (trying to make it running on Motorola 6811)
Op 15-feb-2006, om 23:29 heeft Jeff Johnston het volgende geschreven:


Carl van Denzen wrote:

I am working on a very simple application, but do not know what is the best solution. The documentation is not clear enough (for me).
From the mailing list, the preferred way is NOT to use the _xxxx_r functions. Mention this preference in the docs.
The documentation phrase "Each function which uses the global reentrancy structure uses the global variable _impure_ptr, which points to a reentrancy structure." is confusing. Is there really a GLOBAL reentrancy structure?



Yes. I guess it would be clearer to call it the default reentrancy structure that is of global-scope. It is used by functions that have
both a regular and _r form. The regular form of the function calls the _r version, passing the default reentrancy structure "or" if __DYNAMIC_REENTRANCY__ is set to true, it calls the function __getreent() to get a reentrancy structure which is then passed to the _r version.


This leads to the following choices:

1. With no threading, just let functions use the default reentrancy
struct (i.e. do nothing and don't worry about calling _r routines).
2. Call _r routines only and manually pass an appropriate reentrancy
struct (one allocated per thread).
3. Update the _impure_ptr manually at thread switches and call the
regular forms of functions (i.e. don't worry about calling _r
suffixed functions).
4. Set the __DYNAMIC_REENT__ flag for the platform and
provide a __getreent() function that returns a unique reentrancy
struct for the current running thread. Call regular forms
of functions.


An improvement to the documentation would be an addition to choice 2 (which I think is the preferred choice): "The global _impure_ptr should be set to point to the thread- dependent _reent at every thread switch by the OS".


Actually, I would say choice 4 is the preferred choice for threaded
newlib.


Cheers,
Carl













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