[llvm-objcopy] --dump-section: error if '=' is missing or filename is empty

[MaskRay]

Summary

Fix PR45416: the diagnostic when '=' is missing is misleading.
FileOutputBuffer::create returns successfully when the filename is empty
(the temporary file is .tmp%%%%%%%), but FileOutputBuffer::commit will error when
renaming .tmp%%%%%%% to the empty name).

[jhenderson]

Add a link to the PR.

LGTM otherwise.

llvm/tools/llvm-objcopy/CopyConfig.cpp

703–710

Consider fixing clang-tidy warning whilst you're changing this line.

[jhenderson]

In D101697#2735701, @jhenderson wrote:

Add a link to the PR.

LGTM otherwise.

Apparently, I failed at reading the summary and missed the link there!

[MaskRay]

Fix clang-tidy: warning: 'auto Arg' can be declared as 'auto *Arg' [llvm-qualified-auto]

llvm/test/tools/llvm-objcopy/ELF/dump-section.test

 # EMPTY: 0
 
 # RUN: not llvm-objcopy --dump-section =/dev/null %t /dev/null 2>&1 | \
 # RUN:   FileCheck %s --check-prefix=ERR -DFILE=%t "-DSECTION="
 # RUN: not llvm-objcopy --dump-section .missing=/dev/null %t /dev/null 2>&1 | \
 # RUN:   FileCheck %s --check-prefix=ERR -DFILE=%t -DSECTION=.missing
 
 # ERR: error: '[[FILE]]': section '[[SECTION]]' not found
+
+# RUN: not llvm-objcopy --dump-section .text %t /dev/null 2>&1 | FileCheck %s --check-prefix=ERR2
+# RUN: not llvm-objcopy --dump-section .text= %t /dev/null 2>&1 | FileCheck %s --check-prefix=ERR2
+
+# ERR2: error: bad format for --dump-section, expected section=file

llvm/tools/llvm-objcopy/CopyConfig.cpp

if (!ArgValue.contains('='))
       return createStringError(errc::invalid_argument,
                                "bad format for --add-section: missing '='");
     if (ArgValue.split("=").second.empty())
       return createStringError(
           errc::invalid_argument,
           "bad format for --add-section: missing file name");
     Config.AddSection.push_back(ArgValue);
   }
-  for (auto Arg : InputArgs.filtered(OBJCOPY_dump_section))
-    Config.DumpSection.push_back(Arg->getValue());
+  for (auto *Arg : InputArgs.filtered(OBJCOPY_dump_section)) {
+    StringRef Value(Arg->getValue());
+    if (Value.split('=').second.empty())
+      return createStringError(
+          errc::invalid_argument,
+          "bad format for --dump-section, expected section=file");
+    Config.DumpSection.push_back(Value);
+  }
   Config.StripAll = InputArgs.hasArg(OBJCOPY_strip_all);
   Config.StripAllGNU = InputArgs.hasArg(OBJCOPY_strip_all_gnu);
   Config.StripDebug = InputArgs.hasArg(OBJCOPY_strip_debug);
   Config.StripDWO = InputArgs.hasArg(OBJCOPY_strip_dwo);
   Config.StripSections = InputArgs.hasArg(OBJCOPY_strip_sections);
   Config.StripNonAlloc = InputArgs.hasArg(OBJCOPY_strip_non_alloc);
   Config.StripUnneeded = InputArgs.hasArg(OBJCOPY_strip_unneeded);
   Config.ExtractDWO = InputArgs.hasArg(OBJCOPY_extract_dwo);