Re: [PATCH v2] Makefile: remove the NO_R_TO_GCC_LINKER flag

From: Junio C Hamano <gitster@pobox.com>
Date: May 19, 2019, 00:56 UTC
Message-ID: <xmqqa7fj2ren.fsf@gitster-ct.c.googlers.com>
In-Reply-To: <20190517215847.28179-1-avarab@gmail.com>

Ævar Arnfjörð Bjarmason  <avarab@gmail.com> writes:

Show 16 quoted lines

> It's not needed to simply link to libraries like say libpcre,
> but *only* for those cases where we're linking to such a library not
> present in the OS's library directories. See e.g. ldconfig(8) on Linux
> for more details.
>
> I use this to compile my git with a LIBPCREDIR=$HOME/g/pcre2/inst as
> I'm building that from source, but someone maintaining an OS package
> is almost certainly not going to use this. They're just going to set
> USE_LIBPCRE=YesPlease after installing the libpcre dependency,
> which'll point to OS libraries which ld(1) will find without the help
> of CC_LD_DYNPATH.
> ...
> Our use of "-R" dates back to 455a7f3275 ("More portability.",
> 2005-09-30). Soon after that in bbfc63dd78 ("gcc does not necessarily
> pass runtime libpath with -R", 2006-12-27) the NO_R_TO_GCC flag was
> added, allowing optional use of "-Wl,-rpath=".

Yeah, I recall I had to add -R back when I was with my previous employer, where I had Sun with GNU toolchain as the primary environment and many libraries were custom built outside the system path.

Show 12 quoted lines

> diff --git a/Makefile b/Makefile
> index f965509b3c..ce7a489d64 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -265,10 +265,6 @@ all::
>  #
>  # Define NO_DEFLATE_BOUND if your zlib does not have deflateBound.
>  #
> -# Define NO_R_TO_GCC_LINKER if your gcc does not like "-R/path/lib"
> -# that tells runtime paths to dynamic libraries;
> -# "-Wl,-rpath=/path/lib" is used instead.
> -#

I am not sure if -R was a GCC-only thing; we might want to, instead of removing this seciton, replace it with something like

    # Use "CC_LD_DYNPATH = -R" if your compiler uses "-R/path/to/lib"
    # to specify the runtime paths to dynamic libraries.  These days,
    # GCC uses -Wl,-rpath=/path/to/lib and that is used by default
    # instead.

to help those whose build suddenly starts breaking.

   >  # Define NO_NORETURN if using buggy versions of gcc 4.6+ and profile feedback,

Show 6 quoted lines

>  # as the compiler can crash (http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49299)
>  #
> @@ -1160,6 +1156,7 @@ endif
>  # which'll override these defaults.
>  CFLAGS = -g -O2 -Wall
>  LDFLAGS =

Or it could be a single liner at this point in the file, perhaps

    # Really old GCC used "CC_LD_DYNPATH = -R" for the runtime dynlib path

> +CC_LD_DYNPATH = -Wl,-rpath,