Hmmm, what is the definition of __ctors_start?
I doubt it is an extern variable pointer to void. It is a constant value. Or
more precisely it is no lvalue. There is no memory location where its value is
stored. It just has a value, is a linker generated 'constant' reference.
But by your extern definition, the compiler doesn't know this. It assumes that
it is a normal pointer variable. So later, when you use __ctors_start, the
compiler uses an additional inference, as the value of a variable is
the value stored at the location it references, not the value it actually HAS.
In other words (example):
if __ctors_start is 0x5c00, the line
ctor_t ctor = __ctors_start; results in
mov &0x5c00, &ctor;
moving the value at the begin of Flash into your ctor variable as new pointer,
while what you want is a
mov #0x5c00, &ctor;
moving the VALUE of __ctors_start as new pointer into ctor.
So use &__ctors_start when you want the address __ctors_start points to (the
value of __ctors_start).
JMGross
----- Ursprüngliche Nachricht -----
Von: Tobias Baumgartner
Gesendet am: 20 Okt 2010 16:48:55
I'm currently trying to port a project (using C++) from mspgcc (3.2.3)
to mspgcc4. It is a generic C++ library, running (among other systems)
on top of Contiki (which is a C-based firmware/OS).
As far as I know, constructors of global C++ objects are not called
automatically, so that the user must call them manually. So far I did
this successfully via
typedef void(*ctor_t)();
extern ctor_t __ctors_start;
extern ctor_t __ctors_end;
...
ctor_t ctor = __ctors_start;
while( ctor < __ctors_end )
{
ctor();
ctor = (ctor_t)((void*)ctor + sizeof(void*));
}
However, compiling the project with mspgcc4, it doesn't work anymore.
Printing addresses of ctors_start/end via
printf( "Call ctors from %04x to %04x\n",
(unsigned int)*__ctors_start,
(unsigned int)*__ctors_end );
produces a higher number for ctors start address than for the end
(looking in the *.map-file, everything looks fine).
Do I understand sth wrong (so, is the above code incorrect, and it
worked on the 3.2.3 just "by luck")? Do you have an idea, how I should
call the constructors?
Or is the information above incomplete - then please let me know!
Best,
Tobias
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