rts/PEi386: Fix handling of weak symbols

Previously we would flag the symbol as weak but failed
to set its address, which must be computed from an "auxiliary"
symbol entry the follows the weak symbol.

Fixes #21556.

2 files changed, 13 insertions, 0 deletions

diff --git a/rts/linker/PEi386.c b/rts/linker/PEi386.c
index 82eaaaf226..f6e87dd0e6 100644
--- a/rts/linker/PEi386.c
+++ b/rts/linker/PEi386.c
@@ -1657,6 +1657,13 @@ ocGetNames_PEi386 ( ObjectCode* oc )
       }
       else if (symStorageClass == IMAGE_SYM_CLASS_WEAK_EXTERNAL) {
           isWeak = true;
+          CHECK(getSymNumberOfAuxSymbols (info, sym) == 1);
+          CHECK(symValue == 0);
+          COFF_symbol_aux_weak_external *aux = (COFF_symbol_aux_weak_external *) (sym+1);
+          COFF_symbol* targetSym = &oc->info->symbols[aux->TagIndex];
+          int32_t targetSecNumber = getSymSectionNumber (info, targetSym);
+          Section *targetSection = targetSecNumber > 0 ? &oc->sections[targetSecNumber-1] : NULL;
+          addr = (SymbolAddr*) ((size_t) targetSection->start + getSymValue(info, targetSym));
       }
       else if (  secNumber == IMAGE_SYM_UNDEFINED && symValue > 0) {
          /* This symbol isn't in any section at all, ie, global bss.
diff --git a/rts/linker/PEi386.h b/rts/linker/PEi386.h
index c5c88459a6..cde5974d54 100644
--- a/rts/linker/PEi386.h
+++ b/rts/linker/PEi386.h
@@ -117,6 +117,12 @@ union _COFF_symbol {
     COFF_symbol_ex ex;
 } COFF_symbol;
 
+typedef
+struct {
+    uint32_t TagIndex;
+    uint32_t Characteristics;
+} COFF_symbol_aux_weak_external;
+
 /* A record for storing handles into DLLs. */
 typedef
 struct _OpenedDLL {