Re: [Tinycc-devel] error: Unknown relocation type for got: 23 with -static

[Michael Matz]

Hello,

On Sun, 31 May 2020, Christian Jullien wrote:

> I confirm! I tested this sample with mod on Debian RPi 4 armv7l and had a
> similar error:
>
> $ tcc -static foo.c
> tcc: error: Unknown relocation type for got: 107

This, as well as Scotts problem, are relocations for thread local storage. 
Several facilities of glibc (and other libc's) are implemented as thread 
local variables (e.g. 'errno' is thread local, as well as some management 
structures for the malloc implementation) and when linking statically all 
of these are exposed to TCC.

TCC doesn't implement thread local storage, so that's why there's the 
error.  As long as that's the case static linking against glibc (or any 
other library containing such variables) isn't going to work.

I have a patch somewhere that implements TLS at least for x86-64, maybe I 
find time to dust it off over the next days.  Until then: missing feature 
in TCC with not workaround except not linking statically.

> $ tcc foo.c
>
> -hh help says:
>  -static                       link to static libraries (not recommended)
>
> Why is it not recommended? Because it is not well supported or just because
> shared lib, by ideology, is generally preferred?

I think the comment is indeed about the general recommendation to not link 
statically.  But it should be noted that linking statically against glibc 
specifically is even more discouraged.  I.e. even if you link most of an 
executable statically glibc should stay as shared library dependency.

> My OpenLisp comes in two flavors with gcc: static and shared. When speed
> matters, I recommend the static one which is significantly faster.

A significant performance difference should only happen in fairly special 
circumstances.  Out of couriosity: do you happen to know which ones are 
the case for you?  (E.g. register reduction due to position independend 
code on i386; or function call overhead for do-mostly-nothing functions; 
or something else?)


Ciao,
Michael.

> C.
>
> -----Original Message-----
> From: Tinycc-devel [mailto:tinycc-devel-bounces+eligis=orange.fr@nongnu.org]
> On Behalf Of John Scott
> Sent: Saturday, May 30, 2020 16:55
> To: tinycc-devel@nongnu.org
> Subject: [Tinycc-devel] error: Unknown relocation type for got: 23 with
> -static
>
> Hi,
>
> I was trying to do a build of Tor statically but ran into this issue with
> current master and 0.9.27 package in Debian. I can reproduce with this:
> #include <stdlib.h>
> int main(){ char *p = NULL; free(p); }
>
> and tcc -static gives the error. Is this a bug in tcc or elsewhere?
>
> Sincerely,
> John Scott
>
>
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