[uclibc-ng-devel] [RFC PATCH] elf-{fdpic, dsbt}.h: avoid void pointer's subtraction

Rahul Bedarkar rahul.bedarkar at imgtec.com
Sun Sep 18 09:45:38 CEST 2016


elf-fdpic.h or elf-dsbt.h is included by link.h. When C++ program
includes <link.h>, we get following build failure.

../usr/include/bits/elf-fdpic.h: In function 'void* __reloc_pointer(void*, const elf32_fdpic_loadmap*)':
../usr/include/bits/elf-fdpic.h:95: error: invalid use of 'void'

void pointer addition and subtraction is not allowed in C++ as it has
undetermined size, however in C with language extension it is possible
because sizeof void is treated as one byte.

Instead of performing subtraction on void pointers, typecast it to char*
first.

This build failure is detected by Buildroot autobuilder.
http://autobuild.buildroot.net/results/a10/a10ed48e6eb8411a3d8372f57c05fd11130da0e0/

Signed-off-by: Rahul Bedarkar <rahul.bedarkar at imgtec.com>
---
Note: Compile tested only
---
 libc/sysdeps/linux/bfin/bits/elf-fdpic.h | 2 +-
 libc/sysdeps/linux/c6x/bits/elf-dsbt.h   | 2 +-
 libc/sysdeps/linux/frv/bits/elf-fdpic.h  | 2 +-
 3 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/libc/sysdeps/linux/bfin/bits/elf-fdpic.h b/libc/sysdeps/linux/bfin/bits/elf-fdpic.h
index dddf82c..9fcf93f 100644
--- a/libc/sysdeps/linux/bfin/bits/elf-fdpic.h
+++ b/libc/sysdeps/linux/bfin/bits/elf-fdpic.h
@@ -91,7 +91,7 @@ __reloc_pointer (void *p,
       /* This should be computed as part of the pointer comparison
 	 above, but we want to use the carry in the comparison, so we
 	 can't convert it to an integer type beforehand.  */
-      unsigned long offset = p - (void*)map->segs[c].p_vaddr;
+      unsigned long offset = (char*)p - (char*)map->segs[c].p_vaddr;
       /* We only check for one-past-the-end for the last segment,
 	 assumed to be the data segment, because other cases are
 	 ambiguous in the absence of padding between segments, and
diff --git a/libc/sysdeps/linux/c6x/bits/elf-dsbt.h b/libc/sysdeps/linux/c6x/bits/elf-dsbt.h
index a4e3e7d..0e82ec7 100644
--- a/libc/sysdeps/linux/c6x/bits/elf-dsbt.h
+++ b/libc/sysdeps/linux/c6x/bits/elf-dsbt.h
@@ -94,7 +94,7 @@ __reloc_pointer (void *p,
 
   for (c = 0; c < map->nsegs; c++)
     {
-      unsigned long offset = p - (void*)map->segs[c].p_vaddr;
+      unsigned long offset = (char*)p - (char*)map->segs[c].p_vaddr;
       /* We only check for one-past-the-end for the second segment,
 	 assumed to be the data segment, because other cases are
 	 ambiguous in the absence of padding between segments, and
diff --git a/libc/sysdeps/linux/frv/bits/elf-fdpic.h b/libc/sysdeps/linux/frv/bits/elf-fdpic.h
index dddf82c..9fcf93f 100644
--- a/libc/sysdeps/linux/frv/bits/elf-fdpic.h
+++ b/libc/sysdeps/linux/frv/bits/elf-fdpic.h
@@ -91,7 +91,7 @@ __reloc_pointer (void *p,
       /* This should be computed as part of the pointer comparison
 	 above, but we want to use the carry in the comparison, so we
 	 can't convert it to an integer type beforehand.  */
-      unsigned long offset = p - (void*)map->segs[c].p_vaddr;
+      unsigned long offset = (char*)p - (char*)map->segs[c].p_vaddr;
       /* We only check for one-past-the-end for the last segment,
 	 assumed to be the data segment, because other cases are
 	 ambiguous in the absence of padding between segments, and
-- 
2.6.2



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