[llvm] [FileCheck] Fix parsing empty global and pseudo variable names (PR #82595)

[Daniil Kovalev via llvm-commits]

https://github.com/kovdan01 updated https://github.com/llvm/llvm-project/pull/82595

>From 9a1f4db3f9ccc92c7ad340c04bcabd55a9b1ac3d Mon Sep 17 00:00:00 2001
From: Daniil Kovalev <dkovalev at accesssoftek.com>
Date: Thu, 22 Feb 2024 10:33:55 +0300
Subject: [PATCH 1/2] [FileCheck] Fix parsing empty global and pseudo variable
 names

In `Pattern::parseVariable`, for global variables (those starting with
'$') and for pseudo variables (those starting with '@') the first
character is consumed before actual variable name parsing. If the name
is empty, it leads to out-of-bound access to the corresponding
`StringRef`.

This patch adds an if statement against the case described.
---
 llvm/lib/FileCheck/FileCheck.cpp | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/llvm/lib/FileCheck/FileCheck.cpp b/llvm/lib/FileCheck/FileCheck.cpp
index 6d3a2b9cf46f7c..bb1855f599a1a3 100644
--- a/llvm/lib/FileCheck/FileCheck.cpp
+++ b/llvm/lib/FileCheck/FileCheck.cpp
@@ -297,6 +297,12 @@ Pattern::parseVariable(StringRef &Str, const SourceMgr &SM) {
   if (Str[0] == '$' || IsPseudo)
     ++I;
 
+  if (I == Str.size())
+    return ErrorDiagnostic::get(SM, Str,
+                                StringRef("empty ") +
+                                    (IsPseudo ? "pseudo " : "global ") +
+                                    "variable name");
+
   if (!isValidVarNameStart(Str[I++]))
     return ErrorDiagnostic::get(SM, Str, "invalid variable name");
 

>From efd7bd8734ee517bf3e7f94bb04fed857c4c0fce Mon Sep 17 00:00:00 2001
From: Daniil Kovalev <dkovalev at accesssoftek.com>
Date: Thu, 22 Feb 2024 14:22:25 +0300
Subject: [PATCH 2/2] Add test cases

---
 llvm/test/FileCheck/empty-variable-name.txt | 32 +++++++++++++++++++++
 1 file changed, 32 insertions(+)
 create mode 100644 llvm/test/FileCheck/empty-variable-name.txt

diff --git a/llvm/test/FileCheck/empty-variable-name.txt b/llvm/test/FileCheck/empty-variable-name.txt
new file mode 100644
index 00000000000000..d4c32e0b167d4c
--- /dev/null
+++ b/llvm/test/FileCheck/empty-variable-name.txt
@@ -0,0 +1,32 @@
+a
+
+; RUN: not FileCheck -input-file %s %s 2>&1 | \
+; RUN:   FileCheck -check-prefix CHECK-ERROR -DDIR=%S \
+; RUN:   --match-full-lines --strict-whitespace %s
+
+; CHECK:        a[[]]
+; CHECK-ERROR:[[DIR]]/empty-variable-name.txt:7:13: error: empty variable name
+; CHECK-ERROR-NEXT:; CHECK: a{{\[\[\]\]}}
+; CHECK-ERROR-NEXT:            ^
+
+b
+
+; RUN: not FileCheck -input-file %s -check-prefix CHECK-PSEUDO %s 2>&1 | \
+; RUN:   FileCheck -check-prefix CHECK-ERROR-PSEUDO -DDIR=%S \
+; RUN:   --match-full-lines --strict-whitespace %s
+
+; CHECK-PSEUDO: b[[@]]
+; CHECK-ERROR-PSEUDO:[[DIR]]/empty-variable-name.txt:18:20: error: empty pseudo variable name
+; CHECK-ERROR-PSEUDO-NEXT:; CHECK-PSEUDO: b{{\[\[@\]\]}}
+; CHECK-ERROR-PSEUDO-NEXT:                   ^
+
+c
+
+; RUN: not FileCheck -input-file %s -check-prefix CHECK-GLOBAL %s 2>&1 | \
+; RUN:   FileCheck -check-prefix CHECK-ERROR-GLOBAL -DDIR=%S \
+; RUN:   --match-full-lines --strict-whitespace %s
+
+; CHECK-GLOBAL: c[[$]]
+; CHECK-ERROR-GLOBAL:[[DIR]]/empty-variable-name.txt:29:20: error: empty global variable name
+; CHECK-ERROR-GLOBAL-NEXT:; CHECK-GLOBAL: c{{\[\[\$\]\]}}
+; CHECK-ERROR-GLOBAL-NEXT:                   ^