[objcopy] Return an error in case of an invalid regex (#74319)

As of now, llvm-objcopy silently ignores a provided regex if it doesn't
compile.

This patch adds returning an error saying that a regex couldn't be
compiled, along with the compilation error message.

---------

Co-authored-by: James Henderson <[email protected]>

Author: kuilpd

llvm/lib/ObjCopy/CommonConfig.cpp

@@ -7,6 +7,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "llvm/ObjCopy/CommonConfig.h"
+#include "llvm/Support/Errc.h"
 
 namespace llvm {
 namespace objcopy {
@@ -38,6 +39,12 @@ NameOrPattern::create(StringRef Pattern, MatchStyle MS,
                          IsPositiveMatch);
   }
   case MatchStyle::Regex: {
+    Regex RegEx(Pattern);
+    std::string Err;
+    if (!RegEx.isValid(Err))
+      return createStringError(errc::invalid_argument,
+                               "cannot compile regular expression \'" +
+                                   Pattern + "\': " + Err);
     SmallVector<char, 32> Data;
     return NameOrPattern(std::make_shared<Regex>(
         ("^" + Pattern.ltrim('^').rtrim('$') + "$").toStringRef(Data)));

llvm/test/tools/llvm-objcopy/regex-error.test

@@ -0,0 +1,13 @@
+## Test if providing objcopy with an invalid regex generates an error.
+
+# RUN: yaml2obj %s -o %t
+
+# RUN: not llvm-objcopy --regex --strip-symbol='[^)\' %t /dev/null 2>&1 | FileCheck %s
+# CHECK: error: cannot compile regular expression '[^)\'
+
+!ELF
+FileHeader:
+  Class:   ELFCLASS64
+  Data:    ELFDATA2LSB
+  Type:    ET_EXEC
+  Machine: EM_X86_64