COFF: Fix import symbol name mangling.

For IMPORT_NAME_NOPREFIX symbols, we should remove only one prefix character.

llvm-svn: 241854

lld/COFF/InputFiles.cpp

@@ -249,6 +249,12 @@ MachineTypes ObjectFile::getMachineType() {
   return IMAGE_FILE_MACHINE_UNKNOWN;
 }
 
+StringRef ltrim1(StringRef S, const char *Chars) {
+  if (!S.empty() && strchr(Chars, S[0]))
+    return S.substr(1);
+  return S;
+}
+
 std::error_code ImportFile::parse() {
   const char *Buf = MB.getBufferStart();
   const char *End = MB.getBufferEnd();
@@ -273,10 +279,10 @@ std::error_code ImportFile::parse() {
     ExtName = Name;
     break;
   case IMPORT_NAME_NOPREFIX:
-    ExtName = Name.ltrim("?@_");
+    ExtName = ltrim1(Name, "?@_");
     break;
   case IMPORT_NAME_UNDECORATE:
-    ExtName = Name.ltrim("?@_");
+    ExtName = ltrim1(Name, "?@_");
     ExtName = ExtName.substr(0, ExtName.find('@'));
     break;
   }

lld/test/COFF/imports-mangle.test

@@ -5,7 +5,7 @@
 
 # CHECK: Import {
 # CHECK:   Symbol: sym4 (0)
-# CHECK:   Symbol: sym3 (1)
+# CHECK:   Symbol: _sym3 (1)
 # CHECK:   Symbol: sym1 (2)
 # CHECK:   Symbol:  (2)
 # CHECK: }
@@ -51,7 +51,7 @@ symbols:
     SimpleType:      IMAGE_SYM_TYPE_NULL
     ComplexType:     IMAGE_SYM_DTYPE_FUNCTION
     StorageClass:    IMAGE_SYM_CLASS_EXTERNAL
-  - Name:            _sym3
+  - Name:            __sym3
     Value:           0
     SectionNumber:   0
     SimpleType:      IMAGE_SYM_TYPE_NULL