Re: [RFC][PATCH v1 1/5] bits/dlfcn.h: Declare and describe the dlmopen RTLD_SHARED flag

[Carlos O'Donell <carlos at redhat dot com>]

On 05/16/2018 01:11 PM, Vivek Das Mohapatra wrote:
> From: Vivek Das Mohapatra <vivek@collabora.co.uk>
> 
> This flag will instruct dlmopen to create a shared object present
> in both the main namespace and the selected namespace when set.
> ---
>  bits/dlfcn.h | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/bits/dlfcn.h b/bits/dlfcn.h
> index b0b129b66b..a96270d499 100644
> --- a/bits/dlfcn.h
> +++ b/bits/dlfcn.h
> @@ -32,6 +32,13 @@
>     visible as if the object were linked directly into the program.  */
>  #define RTLD_GLOBAL	0x00100
>  
> +/* If the following bit is set in the MODE argument to dlmopen
> +   then the target object is loaded into the main namespace (if
> +   it is not already there) and a shallow copy (clone) is placed
> +   in the target namespace: This allows multiple namespaces to
> +   share a single instance of a DSO.  */
> +#define RTLD_SHARED 0x00080

This is an RFC, but also note there is a MIPS-specific dlfcn.h which needs
patching also to define RTLD_SHARED. We should probably try to look at how
the constants overlap, and find a common value to start with for everyone.

I agree that we need a constant with which to choose between:

* Old dlmopen behaviour.

* New dlmopen behaviour.

> +
>  /* Unix98 demands the following flag which is the inverse to RTLD_GLOBAL.
>     The implementation does this by default and so we can define the
>     value to zero.  */
> 


-- 
Cheers,
Carlos.