[PATCH] gdb: make {fill, supply}_{g, fp}regset() as weak functions in gregset.h

[PATCH] gdb: make {fill, supply}_{g, fp}regset() as weak functions in gregset.h

[Tiezhu Yang]

I am working on the gdb support for LoongArch (a new RISC Architecture),
when build with gdb/loongarch-tdep.c, there exists the following build
error:

      CXXLD  gdb
    /usr/bin/ld: proc-service.o: in function `.LVL73':
    proc-service.c:(.text+0x31c): undefined reference to `fill_gregset(regcache const*, unsigned long (*) [45], int)'
    /usr/bin/ld: proc-service.o: in function `.LM151':
    proc-service.c:(.text+0x35c): undefined reference to `supply_gregset(regcache*, unsigned long const (*) [45])'
    /usr/bin/ld: proc-service.o: in function `.LVL89':
    proc-service.c:(.text+0x3bc): undefined reference to `fill_fpregset(regcache const*, elf_fpreg_t (*) [34], int)'
    /usr/bin/ld: proc-service.o: in function `.LM179':
    proc-service.c:(.text+0x3fc): undefined reference to `supply_fpregset(regcache*, elf_fpreg_t const (*) [34])'
    collect2: error: ld returned 1 exit status

I notice that the above undefined references need to be defined in
gdb/loongarch-linux-nat.c in the future work, but it is better to
declare them as weak functions so that it can build successful now.

Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
---
 gdb/gregset.h | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/gdb/gregset.h b/gdb/gregset.h
index 4b10692..42d752a 100644
--- a/gdb/gregset.h
+++ b/gdb/gregset.h
@@ -31,6 +31,8 @@
 #define GDB_FPREGSET_T fpregset_t
 #endif
 
+#define __weak __attribute__((weak))
+
 typedef GDB_GREGSET_T gdb_gregset_t;
 typedef GDB_FPREGSET_T gdb_fpregset_t;
 
@@ -46,18 +48,18 @@ struct regcache;
 /* Copy register values from the native target gregset/fpregset
    into GDB's internal register cache.  */
 
-extern void supply_gregset (struct regcache *regcache,
+__weak void supply_gregset (struct regcache *regcache,
 			    const gdb_gregset_t *gregs);
-extern void supply_fpregset (struct regcache *regcache,
+__weak void supply_fpregset (struct regcache *regcache,
 			     const gdb_fpregset_t *fpregs);
 
 /* Copy register values from GDB's register cache into
    the native target gregset/fpregset.  If regno is -1, 
    copy all the registers.  */
 
-extern void fill_gregset (const struct regcache *regcache,
+__weak void fill_gregset (const struct regcache *regcache,
 			  gdb_gregset_t *gregs, int regno);
-extern void fill_fpregset (const struct regcache *regcache,
+__weak void fill_fpregset (const struct regcache *regcache,
 			   gdb_fpregset_t *fpregs, int regno);
 
 #endif
-- 
2.1.0

Re: [PATCH] gdb: make {fill, supply}_{g, fp}regset() as weak functions in gregset.h

[Andrew Burgess]

* Tiezhu Yang <yangtiezhu@loongson.cn> [2021-11-11 17:21:00 +0800]:

> I am working on the gdb support for LoongArch (a new RISC Architecture),
> when build with gdb/loongarch-tdep.c, there exists the following build
> error:
> 
>       CXXLD  gdb
>     /usr/bin/ld: proc-service.o: in function `.LVL73':
>     proc-service.c:(.text+0x31c): undefined reference to `fill_gregset(regcache const*, unsigned long (*) [45], int)'
>     /usr/bin/ld: proc-service.o: in function `.LM151':
>     proc-service.c:(.text+0x35c): undefined reference to `supply_gregset(regcache*, unsigned long const (*) [45])'
>     /usr/bin/ld: proc-service.o: in function `.LVL89':
>     proc-service.c:(.text+0x3bc): undefined reference to `fill_fpregset(regcache const*, elf_fpreg_t (*) [34], int)'
>     /usr/bin/ld: proc-service.o: in function `.LM179':
>     proc-service.c:(.text+0x3fc): undefined reference to `supply_fpregset(regcache*, elf_fpreg_t const (*) [34])'
>     collect2: error: ld returned 1 exit status
> 
> I notice that the above undefined references need to be defined in
> gdb/loongarch-linux-nat.c in the future work, but it is better to
> declare them as weak functions so that it can build successful now.

Not approved.

I suspect you are miss-configuring your target.  The proc-service.c
file is added to the build in configure.nat, and this is only done if
your target is configured with "linux" somewhere in its triple.

If your target is (currently) a baremetal target, then don't configure
with "linux" in the triple and proc-service.c will not be built, and
you'll not hit the undefined references.

Obviously, without seeing your full patch set the above is just me
guessing, but there are plenty of non-linux targets in tree, and they
are not running into this same problem, so I'm pretty confident that
this can be fixed without this change.

Thanks,
Andrew



> 
> Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
> ---
>  gdb/gregset.h | 10 ++++++----
>  1 file changed, 6 insertions(+), 4 deletions(-)
> 
> diff --git a/gdb/gregset.h b/gdb/gregset.h
> index 4b10692..42d752a 100644
> --- a/gdb/gregset.h
> +++ b/gdb/gregset.h
> @@ -31,6 +31,8 @@
>  #define GDB_FPREGSET_T fpregset_t
>  #endif
>  
> +#define __weak __attribute__((weak))
> +
>  typedef GDB_GREGSET_T gdb_gregset_t;
>  typedef GDB_FPREGSET_T gdb_fpregset_t;
>  
> @@ -46,18 +48,18 @@ struct regcache;
>  /* Copy register values from the native target gregset/fpregset
>     into GDB's internal register cache.  */
>  
> -extern void supply_gregset (struct regcache *regcache,
> +__weak void supply_gregset (struct regcache *regcache,
>  			    const gdb_gregset_t *gregs);
> -extern void supply_fpregset (struct regcache *regcache,
> +__weak void supply_fpregset (struct regcache *regcache,
>  			     const gdb_fpregset_t *fpregs);
>  
>  /* Copy register values from GDB's register cache into
>     the native target gregset/fpregset.  If regno is -1, 
>     copy all the registers.  */
>  
> -extern void fill_gregset (const struct regcache *regcache,
> +__weak void fill_gregset (const struct regcache *regcache,
>  			  gdb_gregset_t *gregs, int regno);
> -extern void fill_fpregset (const struct regcache *regcache,
> +__weak void fill_fpregset (const struct regcache *regcache,
>  			   gdb_fpregset_t *fpregs, int regno);
>  
>  #endif
> -- 
> 2.1.0
>