[coff] correctly emit safeseh entries for handlers defined in dlls

[inglorion]

Summary

We previously assumed that all SafeSEH handlers are
DefinedRegular symbols. This is not the case for handlers defined in
DLLs. As a result, we were failing to emit entries in the SafeSEH
table for those handlers. This change fixes that.

Fixes PR35324.

[inglorion]

updated test to check for exactly one entry instead of at least one

[inglorion]

updated description to point to bug report

[rnk]

lgtm

No yaml support for import libraries, I take it?

[inglorion]

No yaml support for import libraries, I take it?

Looks that way. There are also a couple of other .libs in the Inputs directory, so I just did the same thing.

[pcc]

In D40102#926937, @inglorion wrote:

No yaml support for import libraries, I take it?

Looks that way. There are also a couple of other .libs in the Inputs directory, so I just did the same thing.

Couldn't you use lld to create an import library?
http://llvm-cs.pcc.me.uk/tools/lld/COFF/Driver.cpp#1115

lld/trunk/COFF/Writer.cpp

if (Config->Machine != I386)
     return;
 
   std::set<Defined *> Handlers;
 
   for (ObjFile *File : ObjFile::Instances) {
     if (!File->SEHCompat)
       return;
     for (Symbol *B : File->SEHandlers) {
-      // Make sure the handler is still live. Assume all handlers are regular
-      // symbols.
-      auto *D = dyn_cast<DefinedRegular>(B);
-      if (D && D->getChunk()->isLive())
-        Handlers.insert(D);
+      // Make sure the handler is still live.
+      if (B->isLive())
+        Handlers.insert(cast<Defined>(B));
     }
   }
 
   if (Handlers.empty())
     return;
 
   SEHTable = make<SEHTableChunk>(Handlers);
   RData->addChunk(SEHTable);

lld/trunk/test/COFF/safeseh-md.s

+# RUN: llvm-mc -triple i686-windows-msvc %s -filetype=obj -o %t.obj
+# RUN: lld-link %t.obj %S/Inputs/except_handler3.lib -safeseh -out:%t.exe -opt:noref -entry:main
+# RUN: llvm-readobj -coff-load-config %t.exe | FileCheck %s
+
+# CHECK: SEHTable [
+# CHECK-NEXT: 0x
+# CHECK-NEXT: ]
+
+        .def     @feat.00;
+        .scl    3;
+        .type   0;
+        .endef
+        .globl  @feat.00
+@feat.00 = 1
+
+        .def     _main;
+        .scl    2;
+        .type   32;
+        .endef
+        .section        .text,"xr",one_only,_main
+        .globl  _main
+_main:
+        movl $42, %eax
+        ret
+
+.safeseh __except_handler3
+
+  .section .rdata,"dr"
+.globl __load_config_used
+__load_config_used:
+        .long 72
+        .fill 60, 1, 0
+        .long ___safe_se_handler_table
+        .long ___safe_se_handler_count