[llvm-readobj][XCOFF] dump the string table only if the size is bigger than 4.

llvm/test/tools/llvm-readobj/XCOFF/string-table.yaml

@@ -32,10 +32,9 @@ Symbols:
 
 ## There is no string table.
 # RUN: yaml2obj --docnum=3 %s -o %t3
-# RUN: llvm-readobj --string-table %t3 2>&1 | FileCheck %s --check-prefix=NO-STRTBL
+# RUN: llvm-readobj --string-table %t3 | FileCheck %s --check-prefix=NO-STRTBL
 
 # NO-STRTBL:      StringTable {
-# NO-STRTBL-NEXT: error: offset is out of string contents
 # NO-STRTBL-NEXT: }
 
 --- !XCOFF

llvm/tools/llvm-readobj/XCOFFDumper.cpp

@@ -462,7 +462,8 @@ void XCOFFDumper::printStringTable() {
   StringRef StrTable = Obj.getStringTable();
   // Print strings from the fifth byte, since the first four bytes contain the
   // length (in bytes) of the string table (including the length field).
-  printAsStringList(StrTable, 4);
+  if (StrTable.size() > 4)
+    printAsStringList(StrTable, 4);
 }
 
 void XCOFFDumper::printDynamicSymbols() {