[llvm-readobj] Improve JSON output

[paulkirth]

Summary

The current implementation outputs JSON in the following way:

[{'<filename>':{'FileSummary':{},...}}]

Using the filename as a key makes processing the JSON data awkward, and
should be avoided. This patch removes that outer key, since the
'FileSummary' data also includes a 'File' field, and so we lose no data.

[paulkirth]

Another option is to replace the removed key with a 'File': <filename> key value pair. Either way will make the output easier to process.

[paulkirth]

I forgot to update tests

[paulkirth]

Update JSON output tests

[jhenderson]

I've added a couple of people who were involved (directly or indirectly) with this feature originally, who may have some comments.

I'm off for a week next week, and have some high priority work I need to finish off before leaving, so haven't got time to review this just yet, but will do so after I'm back.

[jhenderson]

Functionally, this looks good, although I think it might deserve a release note, since anybody relying on the old behaviour will find their parsers stop working.

[paulkirth]

Add release notes.

[paulkirth]

@jhenderson Does the release note seem appropriate?

[jhenderson]

LGTM, with the suggested fixes, thanks!

llvm/docs/ReleaseNotes.rst

181–183

Mostly looks good. I've rephrased it a little, an made a minor edit ot the example, to help with clarity. In the example, I've added a file extension to the filename, to make it more obviously a filename.

187

Nit: not sure you want the double blank line.

[paulkirth]

Update release notes w/ reviewer feedback

[paulkirth]

Remove extra newline

llvm/docs/ReleaseNotes.rst

 Changes to the Debug Info
 ---------------------------------
 
 During this release ...
 
 Changes to the LLVM tools
 ---------------------------------
 
+* ``llvm-readobj --elf-output-style=JSON`` no longer prefixes each JSON object
+  with the file name. Previously, each object file's output looked like
+  ``"main.o":{"FileSummary":{"File":"main.o"},...}`` but is now
+  ``{"FileSummary":{"File":"main.o"},...}``. This allows each JSON object to be
+  parsed in the same way, since each object no longer has a unique key. Tools
+  that consume ``llvm-readobj``'s JSON output should update their parsers
+  accordingly.
+
 Changes to LLDB
 ---------------------------------
 
 Changes to Sanitizers
 ---------------------
 
 
 Other Changes

llvm/test/tools/llvm-readobj/ELF/file-summary-json.test

 ## Test how we output JSON file summaries.
 
 # RUN: rm -rf %t.dir
 # RUN: mkdir -p %t.dir
 # RUN: yaml2obj %s -o %t.dir/obj
 
 ## Test outputting file summary for a single file.
 # RUN: llvm-readobj --elf-output-style=JSON --pretty-print %t.dir/obj | \
 # RUN:   FileCheck %s --check-prefix=SINGLE \
 # RUN:     --match-full-lines --strict-whitespace --implicit-check-not={{.}}
 
 #      SINGLE:[
 # SINGLE-NEXT:  {
-# SINGLE-NEXT:    "{{.*}}/obj": {
-# SINGLE-NEXT:      "FileSummary": {
-# SINGLE-NEXT:        "File": "{{.*}}/obj",
-# SINGLE-NEXT:        "Format": "elf64-x86-64",
-# SINGLE-NEXT:        "Arch": "x86_64",
-# SINGLE-NEXT:        "AddressSize": "64bit",
-# SINGLE-NEXT:        "LoadName": "<Not found>"
-# SINGLE-NEXT:      }
-# SINGLE-NEXT:    }
-# SINGLE-NEXT:  }
+# SINGLE-NEXT:    "FileSummary": {
+# SINGLE-NEXT:      "File": "{{.*}}/obj",
+# SINGLE-NEXT:      "Format": "elf64-x86-64",
+# SINGLE-NEXT:      "Arch": "x86_64",
+# SINGLE-NEXT:      "AddressSize": "64bit",
+# SINGLE-NEXT:      "LoadName": "<Not found>"
+# SINGLE-NEXT:    }
+# SINGLE-NEXT:  }
 # SINGLE-NEXT:]
 
 ## Test outputting file summary for multiple files.
 # RUN: llvm-readobj --elf-output-style=JSON --pretty-print %t.dir/obj %t.dir/obj | \
 # RUN:   FileCheck %s --check-prefix=MULTI \
 # RUN:     --match-full-lines --strict-whitespace --implicit-check-not={{.}}
 
 #      MULTI:[
 # MULTI-NEXT:  {
-# MULTI-NEXT:    "{{.*}}/obj": {
-# MULTI-NEXT:      "FileSummary": {
-# MULTI-NEXT:        "File": "{{.*}}/obj",
-# MULTI-NEXT:        "Format": "elf64-x86-64",
-# MULTI-NEXT:        "Arch": "x86_64",
-# MULTI-NEXT:        "AddressSize": "64bit",
-# MULTI-NEXT:        "LoadName": "<Not found>"
-# MULTI-NEXT:      }
-# MULTI-NEXT:    }
+# MULTI-NEXT:    "FileSummary": {
+# MULTI-NEXT:      "File": "{{.*}}/obj",
+# MULTI-NEXT:      "Format": "elf64-x86-64",
+# MULTI-NEXT:      "Arch": "x86_64",
+# MULTI-NEXT:      "AddressSize": "64bit",
+# MULTI-NEXT:      "LoadName": "<Not found>"
+# MULTI-NEXT:    }
 # MULTI-NEXT:  },
 # MULTI-NEXT:  {
-# MULTI-NEXT:    "{{.*}}/obj": {
-# MULTI-NEXT:      "FileSummary": {
-# MULTI-NEXT:        "File": "{{.*}}/obj",
-# MULTI-NEXT:        "Format": "elf64-x86-64",
-# MULTI-NEXT:        "Arch": "x86_64",
-# MULTI-NEXT:        "AddressSize": "64bit",
-# MULTI-NEXT:        "LoadName": "<Not found>"
-# MULTI-NEXT:      }
-# MULTI-NEXT:    }
-# MULTI-NEXT:  }
+# MULTI-NEXT:    "FileSummary": {
+# MULTI-NEXT:      "File": "{{.*}}/obj",
+# MULTI-NEXT:      "Format": "elf64-x86-64",
+# MULTI-NEXT:      "Arch": "x86_64",
+# MULTI-NEXT:      "AddressSize": "64bit",
+# MULTI-NEXT:      "LoadName": "<Not found>"
+# MULTI-NEXT:    }
+# MULTI-NEXT:  }
 # MULTI-NEXT:]
 
 ## Test outputting file summary for an archive with a single file.
 # RUN: rm -f %t.archive-single
 # RUN: llvm-ar rc %t.archive-single %t.dir/obj
 # RUN: llvm-readobj --elf-output-style=JSON --pretty-print %t.archive-single | \
 # RUN:   FileCheck %s --check-prefix=ARCH-SINGLE \
 # RUN:     --match-full-lines --strict-whitespace --implicit-check-not={{.}}
 
 #      ARCH-SINGLE:[
 # ARCH-SINGLE-NEXT:  {
-# ARCH-SINGLE-NEXT:    "{{.*}}.archive-single(obj)": {
-# ARCH-SINGLE-NEXT:      "FileSummary": {
-# ARCH-SINGLE-NEXT:        "File": "{{.*}}.archive-single(obj)",
-# ARCH-SINGLE-NEXT:        "Format": "elf64-x86-64",
-# ARCH-SINGLE-NEXT:        "Arch": "x86_64",
-# ARCH-SINGLE-NEXT:        "AddressSize": "64bit",
-# ARCH-SINGLE-NEXT:        "LoadName": "<Not found>"
-# ARCH-SINGLE-NEXT:      }
-# ARCH-SINGLE-NEXT:    }
-# ARCH-SINGLE-NEXT:  }
+# ARCH-SINGLE-NEXT:    "FileSummary": {
+# ARCH-SINGLE-NEXT:      "File": "{{.*}}.archive-single(obj)",
+# ARCH-SINGLE-NEXT:      "Format": "elf64-x86-64",
+# ARCH-SINGLE-NEXT:      "Arch": "x86_64",
+# ARCH-SINGLE-NEXT:      "AddressSize": "64bit",
+# ARCH-SINGLE-NEXT:      "LoadName": "<Not found>"
+# ARCH-SINGLE-NEXT:    }
+# ARCH-SINGLE-NEXT:  }
 # ARCH-SINGLE-NEXT:]
 
 ## Test outputting file summary for an archive with multiple files.
 # RUN: rm -f %t.archive-multiple
 # RUN: llvm-ar rc %t.archive-multiple %t.dir/obj %t.dir/obj
 # RUN: llvm-readobj --elf-output-style=JSON --pretty-print %t.archive-multiple | \
 # RUN:   FileCheck %s --check-prefix=ARCH-MULTI \
 # RUN:     --match-full-lines --strict-whitespace --implicit-check-not={{.}}
 
 #      ARCH-MULTI:[
 # ARCH-MULTI-NEXT:  {
-# ARCH-MULTI-NEXT:    "{{.*}}.archive-multiple(obj)": {
-# ARCH-MULTI-NEXT:      "FileSummary": {
-# ARCH-MULTI-NEXT:        "File": "{{.*}}.archive-multiple(obj)",
-# ARCH-MULTI-NEXT:        "Format": "elf64-x86-64",
-# ARCH-MULTI-NEXT:        "Arch": "x86_64",
-# ARCH-MULTI-NEXT:        "AddressSize": "64bit",
-# ARCH-MULTI-NEXT:        "LoadName": "<Not found>"
-# ARCH-MULTI-NEXT:      }
-# ARCH-MULTI-NEXT:    }
+# ARCH-MULTI-NEXT:    "FileSummary": {
+# ARCH-MULTI-NEXT:      "File": "{{.*}}.archive-multiple(obj)",
+# ARCH-MULTI-NEXT:      "Format": "elf64-x86-64",
+# ARCH-MULTI-NEXT:      "Arch": "x86_64",
+# ARCH-MULTI-NEXT:      "AddressSize": "64bit",
+# ARCH-MULTI-NEXT:      "LoadName": "<Not found>"
+# ARCH-MULTI-NEXT:    }
 # ARCH-MULTI-NEXT:  },
 # ARCH-MULTI-NEXT:  {
-# ARCH-MULTI-NEXT:    "{{.*}}.archive-multiple(obj)": {
-# ARCH-MULTI-NEXT:      "FileSummary": {
-# ARCH-MULTI-NEXT:        "File": "{{.*}}.archive-multiple(obj)",
-# ARCH-MULTI-NEXT:        "Format": "elf64-x86-64",
-# ARCH-MULTI-NEXT:        "Arch": "x86_64",
-# ARCH-MULTI-NEXT:        "AddressSize": "64bit",
-# ARCH-MULTI-NEXT:        "LoadName": "<Not found>"
-# ARCH-MULTI-NEXT:      }
-# ARCH-MULTI-NEXT:    }
-# ARCH-MULTI-NEXT:  }
+# ARCH-MULTI-NEXT:    "FileSummary": {
+# ARCH-MULTI-NEXT:      "File": "{{.*}}.archive-multiple(obj)",
+# ARCH-MULTI-NEXT:      "Format": "elf64-x86-64",
+# ARCH-MULTI-NEXT:      "Arch": "x86_64",
+# ARCH-MULTI-NEXT:      "AddressSize": "64bit",
+# ARCH-MULTI-NEXT:      "LoadName": "<Not found>"
+# ARCH-MULTI-NEXT:    }
+# ARCH-MULTI-NEXT:  }
 # ARCH-MULTI-NEXT:]
 
 --- !ELF
 FileHeader:
   Class:   ELFCLASS64
   Data:    ELFDATA2LSB
   Type:    ET_REL
   Machine: EM_X86_64

llvm/test/tools/llvm-readobj/ELF/pretty-print.test

 ## Test the JSON pretty-print flag.
 #
 # RUN: yaml2obj %s -o %t.pretty
 
 ## Test JSON with pretty-print off.
 # RUN: llvm-readobj --elf-output-style=JSON %t.pretty | \
 # RUN:   FileCheck %s --check-prefix=NO-PRETTY \
 # RUN:     --strict-whitespace --implicit-check-not={{.}}
 
 #      NO-PRETTY:[
 # NO-PRETTY-SAME:{
-# NO-PRETTY-SAME:"{{.*}}.pretty":{
 # NO-PRETTY-SAME:"FileSummary":{
 # NO-PRETTY-SAME:"File":"{{.*}}.pretty",
 # NO-PRETTY-SAME:"Format":"elf64-x86-64",
 # NO-PRETTY-SAME:"Arch":"x86_64",
 # NO-PRETTY-SAME:"AddressSize":"64bit",
 # NO-PRETTY-SAME:"LoadName":"<Not found>"
 # NO-PRETTY-SAME:}
 # NO-PRETTY-SAME:}
-# NO-PRETTY-SAME:}
 # NO-PRETTY-SAME:]
 
 ## Test JSON with pretty-print on.
 # RUN: llvm-readobj --elf-output-style=JSON --pretty-print %t.pretty | \
 # RUN:   FileCheck %s --check-prefix=PRETTY \
 # RUN:     --match-full-lines --strict-whitespace --implicit-check-not={{.}}
 
 #      PRETTY:[
 # PRETTY-NEXT:  {
-# PRETTY-NEXT:    "{{.*}}.pretty": {
-# PRETTY-NEXT:      "FileSummary": {
-# PRETTY-NEXT:        "File": "{{.*}}.pretty",
-# PRETTY-NEXT:        "Format": "elf64-x86-64",
-# PRETTY-NEXT:        "Arch": "x86_64",
-# PRETTY-NEXT:        "AddressSize": "64bit",
-# PRETTY-NEXT:        "LoadName": "<Not found>"
-# PRETTY-NEXT:      }
-# PRETTY-NEXT:    }
-# PRETTY-NEXT:  }
+# PRETTY-NEXT:    "FileSummary": {
+# PRETTY-NEXT:      "File": "{{.*}}.pretty",
+# PRETTY-NEXT:      "Format": "elf64-x86-64",
+# PRETTY-NEXT:      "Arch": "x86_64",
+# PRETTY-NEXT:      "AddressSize": "64bit",
+# PRETTY-NEXT:      "LoadName": "<Not found>"
+# PRETTY-NEXT:    }
+# PRETTY-NEXT:  }
 # PRETTY-NEXT:]
 
 --- !ELF
 FileHeader:
   Class:   ELFCLASS64
   Data:    ELFDATA2LSB
   Type:    ET_REL
   Machine: EM_X86_64

llvm/tools/llvm-readobj/ELFDumper.cpp

template <class ELFT> void LLVMELFDumper<ELFT>::printMipsABIFlags() {
   W.printFlags("Flags 1", Flags->flags1, makeArrayRef(ElfMipsFlags1));
   W.printHex("Flags 2", Flags->flags2);
 }
 
 template <class ELFT>
 void JSONELFDumper<ELFT>::printFileSummary(StringRef FileStr, ObjectFile &Obj,
                                            ArrayRef<std::string> InputFilenames,
                                            const Archive *A) {
-  FileScope = std::make_unique<DictScope>(this->W, FileStr);
+  FileScope = std::make_unique<DictScope>(this->W);
   DictScope D(this->W, "FileSummary");
   this->W.printString("File", FileStr);
   this->W.printString("Format", Obj.getFileFormatName());
   this->W.printString("Arch", Triple::getArchTypeName(Obj.getArch()));
   this->W.printString(
       "AddressSize",
       std::string(formatv("{0}bit", 8 * Obj.getBytesInAddress())));
   this->printLoadName();
 }