Recommit: Detect incorrect FileCheck variable CLI definition

Summary:
While the backend code of FileCheck relies on definition of variable
from the command-line to have an equal sign '=' and a variable name
before that, the frontend does not actually enforce it. This leads to
FileCheck crashing when invoked with invalid syntax for the -D option.

This patch adds the missing validation in the frontend. It also makes
the -D option an AlwaysPrefix option to be able to detect -D=FOO as
being a define without variable and -D as missing its value.

Copyright:
- Linaro (changes in version 2 of revision D55940)
- GraphCore (changes in later versions)

Reviewers: jdenny

Subscribers: JonChesterfield, hiraditya, kristina, probinson,
llvm-commits

Differential Revision: https://reviews.llvm.org/D55940

llvm-svn: 353173
(cherry picked from LLVM commit a5e233bf798e8045771aa20af0e8b39cb60a6d73)

Author: pow2clk

test/FileCheck/defines.txt

@@ -1,9 +1,25 @@
 ; RUN: FileCheck -DVALUE=10 -input-file %s %s
 ; RUN: not FileCheck -DVALUE=20 -input-file %s %s 2>&1 | FileCheck %s -check-prefix ERRMSG
+; RUN: not FileCheck -DVALUE10 -input-file %s %s 2>&1 | FileCheck %s -check-prefix ERRCLIEQ1
+; RUN: not FileCheck -D -input-file %s %s 2>&1 | FileCheck %s -check-prefix ERRCLIEQ2
+; RUN: not FileCheck -D=10 -input-file %s %s 2>&1 | FileCheck %s -check-prefix ERRCLIVAR1
+; RUN: not FileCheck -D= -input-file %s %s 2>&1 | FileCheck %s -check-prefix ERRCLIVAR2
+; RUN: FileCheck -DVALUE= -check-prefix EMPTY -input-file %s %s 2>&1
 
 Value = 10
 ; CHECK: Value = [[VALUE]]
 
-; ERRMSG: defines.txt:5:10: error: expected string not found in input
+; ERRMSG: defines.txt:[[@LINE-2]]:10: error: expected string not found in input
 ; ERRMSG: defines.txt:1:1: note: with variable "VALUE" equal to "20"
-; ERRMSG: defines.txt:4:1: note: possible intended match here
+; ERRMSG: defines.txt:[[@LINE-5]]:1: note: possible intended match here
+
+; ERRCLIEQ1: Missing equal sign in command-line definition '-DVALUE10'
+
+; ERRCLIEQ2: FileCheck{{[^:]*}}: for the -D option: requires a value!
+
+; ERRCLIVAR1: Missing pattern variable name in command-line definition '-D=10'
+
+; ERRCLIVAR2: Missing pattern variable name in command-line definition '-D='
+
+Empty value = @@
+; EMPTY: Empty value = @[[VALUE]]@

utils/FileCheck/FileCheck.cpp

@@ -70,7 +70,7 @@ static cl::list<std::string> ImplicitCheckNot(
     cl::value_desc("pattern"));
 
 static cl::list<std::string>
-    GlobalDefines("D", cl::Prefix,
+    GlobalDefines("D", cl::AlwaysPrefix,
                   cl::desc("Define a variable to be used in capture patterns."),
                   cl::value_desc("VAR=VALUE"));
 
@@ -1364,8 +1364,25 @@ int main(int argc, char **argv) {
   /// VariableTable - This holds all the current filecheck variables.
   StringMap<StringRef> VariableTable;
 
-  for (const auto &Def : GlobalDefines)
-    VariableTable.insert(StringRef(Def).split('='));
+  bool GlobalDefineError = false;
+  for (const auto &G : GlobalDefines) {
+    size_t EqIdx = G.find('=');
+    if (EqIdx == std::string::npos) {
+      errs() << "Missing equal sign in command-line definition '-D" << G
+             << "'\n";
+      GlobalDefineError = true;
+      continue;
+    }
+    if (EqIdx == 0) {
+      errs() << "Missing pattern variable name in command-line definition '-D"
+             << G << "'\n";
+      GlobalDefineError = true;
+      continue;
+    }
+    VariableTable.insert(StringRef(G).split('='));
+  }
+  if (GlobalDefineError)
+    return 2;
 
   bool hasError = false;