binutils for musl

binutils for musl

[程智星]

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hi，friend：

When I use Musl as the base library to compile the yocto embedded system, the following error will be reported:

= {anonymous}::Target_i386; Scan = {anonymous}::Target_i386::Scan; Classify_reloc = {anonymous}::Target_i386::Classify_reloc; size_t = long unsigned int]':

| ../../gold/i386.cc:2624:19:   required from here

| ../../gold/gc.h:250:34: error: invalid cast from type 'std::nullptr_t' to type 'gold::Relobj*'

|   250 |   (*secvec).push_back(Section_id(reinterpret_cast<Relobj*>(NULL), 0));

|       |                                  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

| ../../gold/gc.h:332:34: error: invalid cast from type 'std::nullptr_t' to type 'gold::Relobj*'

|   332 |   (*secvec).push_back(Section_id(reinterpret_cast<Relobj*>(NULL), 0));




I think the reason for this problem is:

In glibc, NULL is defined as (void *) 0, so reinterpret_cast is used When performs Type conversion, it is legal to convert NULL to Relobj *. But in Musl, NULL is defined as nullptr, while reinterpret_cast is not safe for cast to convert nullptr to a specific pointer type, so compilation will report an error.




So I used static_cast Replace reinterpret_cast , specific patch as attached;  can this  be integrated into our source code? Or do you have a better solution to address this error?

Looking forward to your reply！

[-- Attachment #2: use-static_cast.patch --]
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diff --git a/gold/gc.h b/gold/gc.h
index 6ebd81f3fd0..4a1368f5abe 100644
--- a/gold/gc.h
+++ b/gold/gc.h
@@ -247,7 +247,7 @@ gc_process_relocs(
 	      if (is_ordinary) 
 		(*secvec).push_back(Section_id(src_obj, dst_indx));
 	      else
-		(*secvec).push_back(Section_id(reinterpret_cast<Relobj*>(NULL), 0));
+		(*secvec).push_back(Section_id(static_cast<Relobj*>(NULL), 0));
               // If the target of the relocation is an STT_SECTION symbol,
               // make a note of that by storing -1 in the symbol vector.
               if (lsym.get_st_type() == elfcpp::STT_SECTION)
@@ -329,7 +329,7 @@ gc_process_relocs(
               if (is_ordinary && dst_obj != NULL)
 		(*secvec).push_back(Section_id(dst_obj, dst_indx));
 	      else
-		(*secvec).push_back(Section_id(reinterpret_cast<Relobj*>(NULL), 0));
+		(*secvec).push_back(Section_id(static_cast<Relobj*>(NULL), 0));
               (*symvec).push_back(gsym);
 	      (*addendvec).push_back(std::make_pair(
 					static_cast<long long>(symvalue),

Re: binutils for musl

[Alan Modra]

On Wed, Jul 12, 2023 at 02:29:41PM +0800, 程智星 wrote:
> hi，friend：
> 
> When I use Musl as the base library to compile the yocto embedded system, the following error will be reported:
> 
> = {anonymous}::Target_i386; Scan = {anonymous}::Target_i386::Scan; Classify_reloc = {anonymous}::Target_i386::Classify_reloc; size_t = long unsigned int]':
> 
> | ../../gold/i386.cc:2624:19:   required from here
> 
> | ../../gold/gc.h:250:34: error: invalid cast from type 'std::nullptr_t' to type 'gold::Relobj*'
> 
> |   250 |   (*secvec).push_back(Section_id(reinterpret_cast<Relobj*>(NULL), 0));
> 
> |       |                                  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

This was fixed in git commit b97bd976233e, with the same patch you
posted.

-- 
Alan Modra
Australia Development Lab, IBM