[PATCH] D92902: [llvm-elfabi] Add flag to keep timestamp when output is the same

[Haowei Wu via Phabricator via llvm-commits]

haowei updated this revision to Diff 310698.
haowei marked 4 inline comments as done.
haowei added a comment.

Address review comments.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D92902/new/

https://reviews.llvm.org/D92902

Files:
  llvm/test/tools/llvm-elfabi/preserve-dates.test
  llvm/tools/llvm-elfabi/llvm-elfabi.cpp


Index: llvm/tools/llvm-elfabi/llvm-elfabi.cpp
===================================================================
--- llvm/tools/llvm-elfabi/llvm-elfabi.cpp
+++ llvm/tools/llvm-elfabi/llvm-elfabi.cpp
@@ -57,22 +57,42 @@
                clEnumValN(ELFTarget::ELF64BE, "elf64-big",
                           "64-bit big-endian ELF stub")));
 cl::opt<std::string> BinaryOutputFilePath(cl::Positional, cl::desc("output"));
+cl::opt<bool>
+    PreserveDates("preserve-dates",
+                  cl::desc("preserve the timestamp of the output file "
+                           "if the content is not changed"));
+cl::alias PreserveDatesA("p", cl::desc("Alias for --preserve-dates"),
+                         cl::aliasopt(PreserveDates));
 
 /// writeTBE() writes a Text-Based ELF stub to a file using the latest version
 /// of the YAML parser.
 static Error writeTBE(StringRef FilePath, ELFStub &Stub) {
+  // Write TBE to memory first.
+  std::string TBEStr;
+  raw_string_ostream OutStr(TBEStr);
+  Error YAMLErr = writeTBEToOutputStream(OutStr, Stub);
+  if (YAMLErr)
+    return YAMLErr;
+  OutStr.str();
+
+  if (PreserveDates) {
+    ErrorOr<std::unique_ptr<MemoryBuffer>> BufOrError =
+        MemoryBuffer::getFile(FilePath);
+    if (BufOrError) {
+      // Compare TBE output with existing TBE file.
+      std::unique_ptr<MemoryBuffer> FileReadBuffer = std::move(*BufOrError);
+      // If TBE file unchanged, abort updating.
+      if (FileReadBuffer->getBuffer().equals(TBEStr))
+        return Error::success();
+    }
+  }
+  // Open TBE file for writing.
   std::error_code SysErr;
-
-  // Open file for writing.
   raw_fd_ostream Out(FilePath, SysErr);
   if (SysErr)
     return createStringError(SysErr, "Couldn't open `%s` for writing",
                              FilePath.data());
-  // Write file.
-  Error YAMLErr = writeTBEToOutputStream(Out, Stub);
-  if (YAMLErr)
-    return YAMLErr;
-
+  Out << TBEStr;
   return Error::success();
 }
 
Index: llvm/test/tools/llvm-elfabi/preserve-dates.test
===================================================================
--- /dev/null
+++ llvm/test/tools/llvm-elfabi/preserve-dates.test
@@ -0,0 +1,8 @@
+## Test writing unchanged content to TBE file with --preserve-dates flag.
+
+# RUN: llvm-elfabi --elf %p/Inputs/gnu_hash.so --emit-tbe=%t
+# RUN: touch -m -d "1970-01-01 00:00:00" %t
+# RUN: llvm-elfabi --elf %p/Inputs/gnu_hash.so --emit-tbe=%t --preserve-dates
+# RUN: ls -l %t | FileCheck %s
+
+# CHECK: {{[[:space:]]1970}}


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