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new 67e61b81207 libs/libc/elf: Let a weak undefined symbol stay undefined.
67e61b81207 is described below
commit 67e61b81207f95edd5b17c41141951881d4f6b77
Author: Marco Casaroli <[email protected]>
AuthorDate: Fri Oct 9 01:14:59 2026 +0200
libs/libc/elf: Let a weak undefined symbol stay undefined.
When libelf_symvalue() could not resolve an undefined symbol it failed
the load with ENOENT, also for a weak reference. A static link gives an
unresolved weak symbol the value 0, and code tests it for that, so a
module that only refers weakly to a symbol (for example the
__cxa_pure_virtual of a C++ program) could not be loaded.
Give an unresolved weak symbol the value 0, as the dynamic relocation
path in elf_bind.c already does.
Assisted-by: Claude Code:claude-opus-5-5
Signed-off-by: Marco Casaroli <[email protected]>
---
libs/libc/elf/elf_symbols.c | 12 +++++++++++-
1 file changed, 11 insertions(+), 1 deletion(-)
diff --git a/libs/libc/elf/elf_symbols.c b/libs/libc/elf/elf_symbols.c
index d5f537e3b0e..43c74c3a6bf 100644
--- a/libs/libc/elf/elf_symbols.c
+++ b/libs/libc/elf/elf_symbols.c
@@ -428,10 +428,20 @@ int libelf_symvalue(FAR struct module_s *modp,
nexports);
}
- /* Was the symbol found from any exporter? */
+ /* Was the symbol found from any exporter? A weak reference may
+ * stay undefined; its value is then 0, as in a static link.
+ */
if (symbol == NULL)
{
+ if (ELF_ST_BIND(sym->st_info) == STB_WEAK)
+ {
+ binfo("SHN_UNDEF: weak \"%s\" stays 0\n",
+ loadinfo->iobuffer);
+ sym->st_value = 0;
+ break;
+ }
+
berr("ERROR: SHN_UNDEF: Exported symbol \"%s\" not found\n",
loadinfo->iobuffer);
return -ENOENT;
