[PATCH] D117749: [lld-macho] Add support for -add_empty_section

[Keith Smiley via Phabricator via llvm-commits]

keith created this revision.
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This is a ld64 option equivalent to `-sectcreate seg sect /dev/null`
that's useful for creating sections like the RESTRICT section.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D117749

Files:
  lld/MachO/Driver.cpp
  lld/MachO/Options.td
  lld/test/MachO/sectcreate.s


Index: lld/test/MachO/sectcreate.s
===================================================================
--- lld/test/MachO/sectcreate.s
+++ lld/test/MachO/sectcreate.s
@@ -20,6 +20,9 @@
 # RUN: llvm-objdump -s %t | FileCheck --check-prefix=STRIPPED %s
 # RUN: llvm-readobj --sections %t | FileCheck --check-prefix=STRIPPEDSEC %s
 
+# RUN: %lld -add_empty_section __foo __bar -o %t %t.o
+# RUN: llvm-readobj --sections %t | FileCheck --check-prefix=EMPTYSECTION %s
+
 # CHECK: Contents of section __TEXT,__text:
 # CHECK: Contents of section __DATA,__data:
 # CHECK: my string!.
@@ -40,6 +43,11 @@
 
 # STRIPPEDSEC-NOT: NoDeadStrip
 
+# EMPTYSECTION: Name: __bar
+# EMPTYSECTION: Segment: __foo
+# EMPTYSECTION: Size: 0x0
+# EMPTYSECTION-NOT: Name:
+
 .text
 .global _main
 _main:
Index: lld/MachO/Options.td
===================================================================
--- lld/MachO/Options.td
+++ lld/MachO/Options.td
@@ -252,6 +252,10 @@
     Alias<sectcreate>,
     HelpText<"Alias for -sectcreate">,
     Group<grp_content>;
+def add_empty_section : MultiArg<["-"], "add_empty_section", 2>,
+    MetaVarName<"<segment> <section>">,
+    HelpText<"Create an empty <section> in <segment>">,
+    Group<grp_content>;
 def filelist : Separate<["-"], "filelist">,
     MetaVarName<"<file>">,
     HelpText<"Read names of files to link from <file>">,
Index: lld/MachO/Driver.cpp
===================================================================
--- lld/MachO/Driver.cpp
+++ lld/MachO/Driver.cpp
@@ -1558,6 +1558,12 @@
         inputFiles.insert(make<OpaqueFile>(*buffer, segName, sectName));
     }
 
+    for (const Arg *arg : args.filtered(OPT_add_empty_section)) {
+      StringRef segName = arg->getValue(0);
+      StringRef sectName = arg->getValue(1);
+      inputFiles.insert(make<OpaqueFile>(MemoryBufferRef(), segName, sectName));
+    }
+
     gatherInputSections();
     if (config->callGraphProfileSort)
       extractCallGraphProfile();


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