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Re: Documentation reentrancy


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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