improve error messages

Author: kkent030315

lld/COFF/DriverUtils.cpp

@@ -255,9 +255,13 @@ void LinkerDriver::parseStub(StringRef path) {
   // 1. stub must be greater than or equal to 64 bytes
   // 2. stub must be 8-byte aligned
   // 3. stub must be start with a valid dos signature 'MZ'
-  if (bufferSize < 0x40 || bufferSize % 8 != 0 ||
-      (bufferStart[0] != 'M' || bufferStart[1] != 'Z'))
-    Err(ctx) << "/stub: invalid format for MS-DOS stub file: " << path;
+  if (bufferSize < 0x40)
+    Err(ctx) << "/stub: stub must be greater than or equal to 64 bytes: "
+             << path;
+  if (bufferStart[0] != 'M' || bufferStart[1] != 'Z')
+    Err(ctx) << "/stub: invalid DOS signature: " << path;
+  if (bufferSize % 8 != 0)
+    Err(ctx) << "/stub: stub must be aligned to 8 bytes: " << path;
   ctx.config.stub = std::move(stub);
 }
 

lld/test/COFF/stub.test

@@ -1,6 +1,6 @@
 # RUN: yaml2obj %p/Inputs/ret42.yaml -o %t.obj
 
-# RUN: lld-link /out:%t.exe /entry:main /stub:%p/Inputs/stub512mz %t.obj
+# RUN: lld-link /out:%t.exe /entry:main /stub:%p/Inputs/stub64mz %t.obj
 # RUN: llvm-readobj --file-headers %t.exe | FileCheck -check-prefix=CHECK1 %s
 
 CHECK1: Magic: MZ
@@ -22,12 +22,13 @@ CHECK1: OEMinfo: 0
 CHECK1: AddressOfNewExeHeader: 64
 
 ## Invalid DOS signature (must be `MZ`)
-# RUN: not lld-link /out:%t.exe /entry:main /stub:%p/Inputs/stub512zz %t.obj 2>&1 | FileCheck -check-prefix=CHECK-INVALID %s
+# RUN: not lld-link /out:%t.exe /entry:main /stub:%p/Inputs/stub64zz %t.obj 2>&1 | FileCheck -check-prefix=CHECK2 %s
+# CHECK2: lld-link: error: /stub: invalid DOS signature: {{.*}}
 
 ## Unaligned stub (must be aligned to 8)
-# RUN: not lld-link /out:%t.exe /entry:main /stub:%p/Inputs/stub516mz %t.obj 2>&1 | FileCheck -check-prefix=CHECK-INVALID %s
+# RUN: not lld-link /out:%t.exe /entry:main /stub:%p/Inputs/stub68mz %t.obj 2>&1 | FileCheck -check-prefix=CHECK3 %s
+# CHECK3: lld-link: error: /stub: stub must be aligned to 8 bytes: {{.*}}
 
-## Too-small stub (must be at least 64 bytes long)
-# RUN: not lld-link /out:%t.exe /entry:main /stub:%p/Inputs/stub511mz %t.obj 2>&1 | FileCheck -check-prefix=CHECK-INVALID %s
-
-# CHECK-INVALID: lld-link: error: /stub: invalid format for MS-DOS stub file: {{.*}}
+## Too-small stub (must be at least 64 bytes long) && Unaligned
+# RUN: not lld-link /out:%t.exe /entry:main /stub:%p/Inputs/stub63mz %t.obj 2>&1 | FileCheck -check-prefix=CHECK4 %s
+# CHECK4: lld-link: error: /stub: stub must be greater than or equal to 64 bytes: {{.*}}