Warn on nonexistent comdat sections in an /order file.

I didn't implement the feature in the original patch because I didn't
come up with an idea to do that easily and efficiently. Turned out that
that is actually easy to implement.

In this patch, we collect comdat sections before gc is run and warn on
nonexistent symbols in an order file.

Differential Revision: https://reviews.llvm.org/D42658

llvm-svn: 323699

2 files changed, 30 insertions, 5 deletions

diff --git a/lld/COFF/Driver.cpp b/lld/COFF/Driver.cpp
index 1b86fe96a31..068074a7b98 100644
--- a/lld/COFF/Driver.cpp
+++ b/lld/COFF/Driver.cpp
@@ -768,6 +768,13 @@ static void parseOrderFile(StringRef Arg) {
     return;
   }
 
+  // Get a list of all comdat sections for error checking.
+  DenseSet<StringRef> Set;
+  for (Chunk *C : Symtab->getChunks())
+    if (auto *Sec = dyn_cast<SectionChunk>(C))
+      if (Sec->Sym)
+        Set.insert(Sec->Sym->getName());
+
   // Open a file.
   StringRef Path = Arg.substr(1);
   std::unique_ptr<MemoryBuffer> MB = CHECK(
@@ -780,7 +787,11 @@ static void parseOrderFile(StringRef Arg) {
   for (std::string S : args::getLines(MB->getMemBufferRef())) {
     if (Config->Machine == I386 && !isDecorated(S))
       S = "_" + S;
-    Config->Order[S] = INT_MIN + Config->Order.size();
+
+    if (Set.count(S) == 0)
+      warn("/order:" + Arg + ": missing symbol: " + S);
+    else
+      Config->Order[S] = INT_MIN + Config->Order.size();
   }
 }
 
@@ -1188,10 +1199,6 @@ void LinkerDriver::link(ArrayRef<const char *> ArgsArr) {
     }
   }
 
-  // Handle /order
-  if (auto *Arg = Args.getLastArg(OPT_order))
-    parseOrderFile(Arg->getValue());
-
   // Handle /export
   for (auto *Arg : Args.filtered(OPT_export)) {
     Export E = parseExport(Arg->getValue());
@@ -1391,6 +1398,12 @@ void LinkerDriver::link(ArrayRef<const char *> ArgsArr) {
   if (Config->Manifest == Configuration::SideBySide)
     createSideBySideManifest();
 
+  // Handle /order. We want to do this at this moment because we
+  // need a complete list of comdat sections to warn on nonexistent
+  // functions.
+  if (auto *Arg = Args.getLastArg(OPT_order))
+    parseOrderFile(Arg->getValue());
+
   // Identify unreferenced COMDAT sections.
   if (Config->DoGC)
     markLive(Symtab->getChunks());
diff --git a/lld/test/COFF/order.test b/lld/test/COFF/order.test
index 25df87d7dba..a01f820e784 100644
--- a/lld/test/COFF/order.test
+++ b/lld/test/COFF/order.test
@@ -24,6 +24,18 @@
 # DEFAULT: fn4
 # DEFAULT: fn1
 
+# RUN: echo fn1 > %t2.order
+# RUN: echo fn2 >> %t2.order
+# RUN: echo fn3 >> %t2.order
+# RUN: echo fn4 >> %t2.order
+# RUN: echo foo >> %t2.order
+# RUN: lld-link -entry:fn1 -subsystem:console -debug %t1.obj %t2.obj \
+# RUN:   -out:%t.exe -order:@%t2.order 2>&1 | FileCheck -check-prefix=WARN %s
+# WARN: warning: /order:{{.*}} missing symbol: foo
+# WARN-NOT: f2
+# WARN-NOT: f3
+# WARN-NOT: f4
+
 --- !COFF
 header:
   Machine:         IMAGE_FILE_MACHINE_AMD64