[Patch] Don't call linker when creating pre-compiled header just because you saw a linker option

[Richard Biener]

On November 14, 2017 7:59:18 PM GMT+01:00, Steve Ellcey <sellcey@cavium.com> wrote:
>I am building GCC (and binutils) with --with-sysroot and I build glibc
>in
>that sysroot too.  I want to test GCC using the glibc libraries I just
>built, but by default GCC uses the dynamic linker that is in /lib and
>that
>is loading the "normal" libraries from /lib or /lib64 at runtime and
>not
>the ones from my sysroot.  To address this I ran the GCC testsuite
>with:
>
>make check
>RUNTESTFLAGS="CFLAGS_FOR_TARGET='-Wl,--dynamic-linker=/mylocation/lib/ld-linux-aarch64.so.1
>-Wl,-rpath=/mylocation/lib64'"
>
>But when I do this, I noticed that a number of pch tests fail.  What I
>found
>is that when I run the pch testsuite, it executes:
>
>/home/sellcey/tot/obj/gcc/gcc/xgcc -B/home/sellcey/tot/obj/gcc/gcc/
>./common-1.h -fno-diagnostics-show-caret -fdiagnostics-color=never -O0
>-g -Wl,--dynamic-linker=/mylocation/lib/ld-linux-aarch64.so.1
>-Wl,-rpath=/mylocation/lib64 -o common-1.h.gch
>
>And this causes the linker to run and try to create an executable
>instead of 
>creating a pre-compiled header.  If I run the same command without the
>-Wl flags then GCC creates the pre-compiled header that I need for
>testing.
>
>I tracked this down to driver::maybe_run_linker where it sees the
>linker
>flags and increments num_linker_inputs, this causes the routine to call
>the linker.  I would like to have this function ignore linker options
>and only count linker input files.  This way the linker is only called
>when there is an actual file to link.
>
>I tested this with the GCC testsuite and got no regressions, OK to
>checkin?

I think the intent is to link even for just - lfoo while it makes sense to ignore -L/path - Wl,... Certainly counts as possible input. 

It seems you even break - lfoo. 

Richard. 

>
>2017-11-14  Steve Ellcey  <sellcey@cavium.com>
>
>	* gcc.c (driver::maybe_run_linker): Ignore linker options
>	when checking for linker inputs.
>
>
>diff --git a/gcc/gcc.c b/gcc/gcc.c
>index 43e6d59..61c7561 100644
>--- a/gcc/gcc.c
>+++ b/gcc/gcc.c
>@@ -8289,11 +8289,14 @@ driver::maybe_run_linker (const char *argv0)
>const
>   int linker_was_run = 0;
>   int num_linker_inputs;
> 
>-  /* Determine if there are any linker input files.  */
>+  /* Determine if there are any linker input files, but ignore
>+     linker options.  If we have options but no input files we
>+     do not want to call the linker.  */
>   num_linker_inputs = 0;
>   for (i = 0; (int) i < n_infiles; i++)
>-    if (explicit_link_files[i] || outfiles[i] != NULL)
>-      num_linker_inputs++;
>+    if ((explicit_link_files[i] || outfiles[i] != NULL)
>+        && (outfiles[i] == NULL || outfiles[i][0] != '-'))
>+        num_linker_inputs++;
> 
>   /* Run ld to link all the compiler output files.  */
>