Re: [Tinycc-devel] Re : Re: Re : Re: win32: -Wl,-nostdlib: undefined symbol 'memset'

[Michael Matz]

Hello,

On Tue, 12 Sep 2023, avih via Tinycc-devel wrote:

> > Also, what is "pure machine code"? With neither input nor output it
> > couldn't do anything but waste instruction cycles.
>
> A function implemented in machine code, where the input is the
> arguments in whatever calling convention the implementation uses,
> and the output is the return value and whatever memory side effects.
>
> I was hoping that compiling a C function which does not call other
> functions would result in machine code which does not call functions,
> except maybe existing internal compiler functions.
>
> In the example above it probably does not call external functions.
> But the user can't tell when it does and when it doesn't, which makes
> -nostdlib very problematic from a practical point of view.

"Very problematic" seems an exaggeration given that e.g. GCC behaves 
exactly the same, given the right circumstances.  TCC, as GCC, freely 
emits calls to memcpy, memmove and memset.  It did so forever, like GCC. 
If anything then this is a problem of documentation (not for the 
command line help).  TCCs docu is incomplete in many aspects, and this 
isn't the biggest problem by far.

> Even if these are terrible suggestions, the question remains:
> What does the user need to do in order to use -nostdlib?

The user needs to provide a working implementation of memcpy, memmove, 
memset (and abort).

> And maybe also: what is -stdlib good for?

Hmm?  It's the opposite of nostdlib.  And nostdlib is for exactly the 
documented purpose: prevent linking with default startup files and C 
library.  If you're asking what _that_ is for, then: developing software 
that doesn't make use of the usual hosted C environment, like boot 
loaders or OS kernels.  It's a special-case option, not to be used in 
random software development.


Ciao,
Michael.