[LLD] [COFF] Error out if the runtime pseudo relocation function is missing

lld/COFF/Writer.cpp

@@ -2072,8 +2072,16 @@ void Writer::createRuntimePseudoRelocs() {
     return;
   }
 
-  if (!rels.empty())
+  if (!rels.empty()) {
     log("Writing " + Twine(rels.size()) + " runtime pseudo relocations");
+    const char *symbolName = "_pei386_runtime_relocator";
+    Symbol *relocator = ctx.symtab.findUnderscore(symbolName);
+    if (!relocator)
+      error("output image has runtime pseudo relocations, but the function " +
+            Twine(symbolName) +
+            " is missing; it is needed for fixing the relocations at runtime");
+  }
+
   PseudoRelocTableChunk *table = make<PseudoRelocTableChunk>(rels);
   rdataSec->addChunk(table);
   EmptyChunk *endOfList = make<EmptyChunk>();

lld/test/COFF/autoimport-arm-data.s

@@ -33,6 +33,9 @@
     .text
     .thumb
 main:
+    bx lr
+    .global _pei386_runtime_relocator
+_pei386_runtime_relocator:
     bx lr
     .data
 ptr:

lld/test/COFF/autoimport-arm64-data.s

@@ -33,6 +33,9 @@
     .global main
     .text
 main:
+    ret
+    .global _pei386_runtime_relocator
+_pei386_runtime_relocator:
     ret
     .data
 ptr:

lld/test/COFF/autoimport-gnu-implib.s

@@ -27,5 +27,8 @@
     .text
 main:
     movl data(%rip), %eax
+    ret
+    .global _pei386_runtime_relocator
+_pei386_runtime_relocator:
     ret
     .data

lld/test/COFF/autoimport-handler-func.s

@@ -0,0 +1,36 @@
+# REQUIRES: x86
+# RUN: split-file %s %t.dir
+
+# RUN: llvm-dlltool -m i386:x86-64 -d %t.dir/lib.def -D lib.dll -l %t.dir/lib.lib
+
+# RUN: llvm-mc -triple=x86_64-windows-gnu %t.dir/main.s -filetype=obj -o %t.dir/main.obj
+# RUN: llvm-mc -triple=x86_64-windows-gnu %t.dir/func.s -filetype=obj -o %t.dir/func.obj
+# RUN: env LLD_IN_TEST=1 not lld-link -lldmingw -out:%t.dir/main.exe -entry:main %t.dir/main.obj %t.dir/lib.lib 2>&1 | FileCheck %s --check-prefix=ERR
+
+# RUN: lld-link -lldmingw -out:%t.dir/main.exe -entry:main %t.dir/main.obj %t.dir/func.obj %t.dir/lib.lib 2>&1 | FileCheck %s --check-prefix=NOERR --allow-empty
+
+# ERR: error: output image has runtime pseudo relocations, but the function _pei386_runtime_relocator is missing; it is needed for fixing the relocations at runtime
+
+# NOERR-NOT: error
+
+#--- main.s
+    .global main
+    .text
+main:
+    ret
+
+    .data
+    .long 1
+    .quad variable
+    .long 2
+
+#--- func.s
+    .global _pei386_runtime_relocator
+    .text
+_pei386_runtime_relocator:
+    ret
+
+#--- lib.def
+EXPORTS
+variable DATA
+

lld/test/COFF/autoimport-warn.s

@@ -18,6 +18,9 @@ main:
     movl variable2(%rip), %ecx
     addl %ecx, %eax
     ret
+    .global _pei386_runtime_relocator
+_pei386_runtime_relocator:
+    ret
 
     .section .rdata$.refptr.variable1,"dr",discard,.refptr.variable1
     .global .refptr.variable1

lld/test/COFF/autoimport-x86.s

@@ -55,6 +55,9 @@
     .text
 main:
     movl variable(%rip), %eax
+    ret
+    .global _pei386_runtime_relocator
+_pei386_runtime_relocator:
     ret
     .data
 ptr: