[binutils-gdb] ld: entry size and merge/strings attributes propagation

[Jan Beulich]

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=74f045d47ab9060bc4e8b82e62bdf2d0ef730cb5

commit 74f045d47ab9060bc4e8b82e62bdf2d0ef730cb5
Author: Jan Beulich <jbeulich@suse.com>
Date:   Tue Aug 26 10:42:03 2025 +0200

    ld: entry size and merge/strings attributes propagation
    
    While commit 9c0adb10c7fc ("elf: Clear entsize when clearing
    SEC_MERGE|SEC_STRINGS") addressed the particular issue reported in
    PR ld/33291, it didn't go quite far enough to deal with related aspects
    as well:
    
    As indicated in other recent commits, the three properties can be
    largely independent (ELF generally being the target here): Entry size
    doesn't require either of merge/strings, and strings also doesn't
    require merge. Commit 98e6d3f5bd4e ("gas/ELF: allow specifying entity
    size for arbitrary sections") uncovered issues with ld's handling.
    
    Zap entry size when it doesn't match between input sections. In that
    case SEC_MERGE and SEC_STRINGS also need to be removed, as their
    underlying granularity is lost. Then deal with SEC_MERGE and
    SEC_STRINGS separately.
    
    Otoh record entry size from the first input independent of SEC_MERGE.

Diff:
---
 ld/ldlang.c | 26 +++++++++++++++++---------
 1 file changed, 17 insertions(+), 9 deletions(-)

diff --git a/ld/ldlang.c b/ld/ldlang.c
index 0bb4a17df19..54292a8dfe1 100644
--- a/ld/ldlang.c
+++ b/ld/ldlang.c
@@ -2854,15 +2854,24 @@ lang_add_section (lang_statement_list_type *ptr,
       /* Only set SEC_READONLY flag on the first input section.  */
       flags &= ~ SEC_READONLY;
 
-      /* Keep SEC_MERGE and SEC_STRINGS only if they are the same.  */
-      if ((output->bfd_section->flags & (SEC_MERGE | SEC_STRINGS))
-	  != (flags & (SEC_MERGE | SEC_STRINGS))
-	  || ((flags & SEC_MERGE) != 0
-	      && output->bfd_section->entsize != section->entsize))
+      /* Keep entry size, SEC_MERGE, and SEC_STRINGS only if entry sizes are
+	 the same.  */
+      if (output->bfd_section->entsize != section->entsize)
 	{
-	  output->bfd_section->flags &= ~ (SEC_MERGE | SEC_STRINGS);
 	  output->bfd_section->entsize = 0;
-	  flags &= ~ (SEC_MERGE | SEC_STRINGS);
+	  flags &= ~(SEC_MERGE | SEC_STRINGS);
+	}
+
+      /* Keep SEC_MERGE and SEC_STRINGS (each) only if they are the same.  */
+      if ((output->bfd_section->flags ^ flags) & SEC_MERGE)
+	{
+	  output->bfd_section->flags &= ~SEC_MERGE;
+	  flags &= ~SEC_MERGE;
+	}
+      if ((output->bfd_section->flags ^ flags) & SEC_STRINGS)
+	{
+	  output->bfd_section->flags &= ~SEC_STRINGS;
+	  flags &= ~SEC_STRINGS;
 	}
     }
   output->bfd_section->flags |= flags;
@@ -2877,8 +2886,7 @@ lang_add_section (lang_statement_list_type *ptr,
 				     link_info.output_bfd,
 				     output->bfd_section,
 				     &link_info);
-      if ((flags & SEC_MERGE) != 0)
-	output->bfd_section->entsize = section->entsize;
+      output->bfd_section->entsize = section->entsize;
     }
 
   if ((flags & SEC_TIC54X_BLOCK) != 0