undefined reference to __reent_magic

I'm working on some shared library based exporter plugins for SketchBlock.

I've come across this

undefined reference to __reent_magic

error twice now , first time in libjpeg.a second time in libpng.a

It seems to be associated with the error reporting callbacks, in the case of libjpeg I replaced the error code with custom code, but although I could do that with libpng I'd like to work out how to fix this at src.

Naturally I'm building the library with -nostartfiles and opening INewlib for myself in the startup code.

Any ideas on what this symbol does and how to get it into my shared.library ?

Using the libpng.a and libjpeg.a from the SDK. (I think...)

i made a text search for _reent_magic (one underscore at beginning) snside lots of amiga files and it seems used in several binary
Perhaps something like a #include <reent.h> is missing...


Alain

@thellier

__reent_magic (deinetly two underscores ) is not defined in
reent.h or in sys/reent.h . They are included indirectly via stdio etc I think anyway.

It seems to be defined in

newlib/lib/crtbegin.o

Anyone know how to initialise it?

I thought this error was caused by using libraries built for clib2 in a program built for newlib, or vice versa.

Maybe try rebuilding the libraries with the compiler+options you're using for the other code?

@Chris

Quote:

I'm fairly sure I'm using newlib compiled libPNG and the sysmbol does seem to be in the crtbegin.o object so I don;t think it's a mixng clib2 with newlib thing.

I just tried defining the symbol with

uint32 __reent_magic;


in my library init.c and it now links (as it would) but more interesting the png loader now works as expected.

I tried that before with the jpeg lib and it caused crashes, unless the crash was for some other reason, and just a coincidence (there were a few other errors to fix).

Possible work arround, love to hear from someone who "knows"....

it's due newlib/clib2 mixing.

@spotUP

No it's not. At least not in this case.

Yes you would get that error sometimes if you accidentally linked in a newlib based library to a clib2 based project, but in this case I'm not linking against clib2 but newlb.

@broadblues
Quote:
In my SDK the newlib/lib directory contains links to clib2 libraries (libamiga.a & libdebug.a). Is it possible that either of those libs are being linked in unintentionally??

@xenic

Libamiga.a doesn't use any clib functions so it doesn't matter whether you link it with clib2 or newlib. I think the same applies to libdebug.a as well.

@broadblues

The symbol __reent_magic is in crtbegin.o (startup code). It's defined as an alias of SysBase but other than that I don't really know what it's used for.

@salass00

Quote:

hmm so defineing as

struct Library *__reent_magic = (struct Library *)SysBase

somewhere in my code should be enough?

@broadblues

You could also just add:

extern struct Library *__reent_magic __attribute__((alias("SysBase")));

in the same file where you define the SysBase global.

This way they will use the same space in the executable so you won't have to init them separately.

The extern looks weird but is needed because otherwise the alias will only work locally.