[LLD] [MinGW] Look for other library patterns with -l

[mstorsjo]

Summary

GNU ld looks for a number of other patterns than just lib<name>.dll.a and lib<name>.a.

GNU ld does support linking directly against a DLL without using an import library. If that's the only match for a -l argument, point out that the user needs to use an import library, instead of leaving the user with a puzzling message about the -l argument not being found at all.

Also convert an existing case of fatal() into error().

[rnk]

lgtm

[ruiu]

LGTM with this change.

lld/MinGW/Driver.cpp

145–146

It should be error instead of fatal, as our promise is that we use fatal only to report corrupted files.

[mstorsjo]

Changed to use error() instead of fatal() in the added lines of code, and in another place in the same function. Added an if (errorCount()) return false; at the end of the MinGW driver, to avoid actually trying to start the linking if errors were reported at this stage.

All other existing error reporting in the MinGW driver is still using fatal(), but changing that is a different matter.

[ruiu]

LGTM

Using error instead of fatal is not a high priority matter for the MinGW driver because I believe users are using this driver as a command. But still it is better to use error because it is more like a contract as a library. So, can you make a follow-up change?

[mstorsjo]

In D68689#1703104, @ruiu wrote:

LGTM

Using error instead of fatal is not a high priority matter for the MinGW driver because I believe users are using this driver as a command. But still it is better to use error because it is more like a contract as a library. So, can you make a follow-up change?

I can try to make such a change a bit later, yes, but I've got a bit too many other things going on right now.

lld/MinGW/Driver.cpp

 
 // This is for -lfoo. We'll look for libfoo.dll.a or libfoo.a from search paths.
 static std::string
 searchLibrary(StringRef name, ArrayRef<StringRef> searchPaths, bool bStatic) {
   if (name.startswith(":")) {
     for (StringRef dir : searchPaths)
       if (Optional<std::string> s = findFile(dir, name.substr(1)))
         return *s;
-    fatal("unable to find library -l" + name);
+    error("unable to find library -l" + name);
+    return "";
   }
 
   for (StringRef dir : searchPaths) {
-    if (!bStatic)
+    if (!bStatic) {
       if (Optional<std::string> s = findFile(dir, "lib" + name + ".dll.a"))
         return *s;
+      if (Optional<std::string> s = findFile(dir, name + ".dll.a"))
+        return *s;
+    }
     if (Optional<std::string> s = findFile(dir, "lib" + name + ".a"))
       return *s;
+    if (!bStatic) {
+      if (Optional<std::string> s = findFile(dir, name + ".lib"))
+        return *s;
+      if (Optional<std::string> s = findFile(dir, "lib" + name + ".dll")) {
+        error("lld doesn't support linking directly against " + *s +
+              ", use an import library");
+        return "";
+      }
+      if (Optional<std::string> s = findFile(dir, name + ".dll")) {
+        error("lld doesn't support linking directly against " + *s +
+              ", use an import library");
+        return "";
+      }
+    }
   }
-  fatal("unable to find library -l" + name);
+  error("unable to find library -l" + name);
+  return "";
 }
 
 // Convert Unix-ish command line arguments to Windows-ish ones and
 // then call coff::link.
 bool mingw::link(ArrayRef<const char *> argsArr, raw_ostream &diag) {
   MinGWOptTable parser;
   opt::InputArgList args = parser.parse(argsArr.slice(1));
 
bool mingw::link(ArrayRef<const char *> argsArr, raw_ostream &diag) {
 
   if (args.hasArg(OPT__HASH_HASH_HASH))
     return true;
 
   // Repack vector of strings to vector of const char pointers for coff::link.
   std::vector<const char *> vec;
   for (const std::string &s : linkArgs)
     vec.push_back(s.c_str());
+  if (errorCount())
+    return false;
   return coff::link(vec, true);
 }

lld/test/MinGW/lib.test

 RUN: ld.lld -### -m i386pep -Bstatic -lfoo -L%t/lib | FileCheck -check-prefix=LIB4 %s
 LIB4: libfoo.a
 
 RUN: echo > %t/lib/libbar.dll.a
 RUN: echo > %t/lib/libbar.a
 RUN: ld.lld -### -m i386pep -Bstatic -lfoo -Bdynamic -lbar -L%t/lib | FileCheck -check-prefix=LIB5 %s
 LIB5:      libfoo.a
 LIB5-SAME: libbar.dll.a
+
+RUN: echo > %t/lib/noprefix.dll.a
+RUN: echo > %t/lib/msvcstyle.lib
+RUN: ld.lld -### -m i386pep -L%t/lib -lnoprefix -lmsvcstyle | FileCheck -check-prefix=OTHERSTYLES %s
+OTHERSTYLES: noprefix.dll.a
+OTHERSTYLES-SAME: msvcstyle.lib
+
+RUN: echo > %t/lib/libnoimplib.dll
+RUN: echo > %t/lib/noprefix_noimplib.dll
+RUN: not ld.lld -### -m i386pep -L%t/lib -lnoimplib 2>&1 | FileCheck -check-prefix=UNSUPPORTED-DLL1 %s
+RUN: not ld.lld -### -m i386pep -L%t/lib -lnoprefix_noimplib 2>&1 | FileCheck -check-prefix=UNSUPPORTED-DLL2 %s
+UNSUPPORTED-DLL1: lld doesn't support linking directly against {{.*}}libnoimplib.dll, use an import library
+UNSUPPORTED-DLL2: lld doesn't support linking directly against {{.*}}noprefix_noimplib.dll, use an import library