[PATCH] D92052: [MC][ELF] Accept abbreviated form with sh_flags and sh_entsize

[Tobias Burnus via Phabricator via llvm-commits]

burnus created this revision.
burnus added reviewers: grimar, jhenderson, bd1976llvm, psmith, MaskRay.
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burnus requested review of this revision.

D73999 <https://reviews.llvm.org/D73999> / commit 75af9da755721123e62b45cd0bc0c5e688a9722a <https://reviews.llvm.org/rG75af9da755721123e62b45cd0bc0c5e688a9722a>
added for LLVM 10 a check that sh_flags and sh_entsize (and sh_type)
changes are an error, in line with GNU assembler.

      

However, GNU assembler accepts and GCC generates an abbreviated form:
while the first .section contains the flags and entsize, subsequent
sections simply contain the name without repeating entsize or flags.

      

Do likewise for better compatibility.

      

See https://bugs.llvm.org/show_bug.cgi?id=48201


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D92052

Files:
  llvm/lib/MC/MCParser/ELFAsmParser.cpp
  llvm/test/MC/ELF/section-entsize-not-repeated.s
  llvm/test/MC/ELF/section-flags-changed-2.s


Index: llvm/test/MC/ELF/section-flags-changed-2.s
===================================================================
--- /dev/null
+++ llvm/test/MC/ELF/section-flags-changed-2.s
@@ -0,0 +1,14 @@
+# RUN: not llvm-mc -triple=x86_64 %s -o /dev/null 2>&1 | FileCheck %s --implicit-check-not=error:
+
+foo:
+.section .foo,"ax", at progbits
+
+.section .foo
+
+# CHECK: {{.*}}.s:[[# @LINE+1]]:1: error: changed section flags for .foo, expected: 0x6
+.section .foo,"awx", at progbits
+
+# CHECK: {{.*}}.s:[[# @LINE+1]]:1: error: changed section flags for .foo, expected: 0x6
+.pushsection .foo,"a", at progbits
+
+.pushsection .foo
Index: llvm/test/MC/ELF/section-entsize-not-repeated.s
===================================================================
--- /dev/null
+++ llvm/test/MC/ELF/section-entsize-not-repeated.s
@@ -0,0 +1,21 @@
+# RUN: llvm-mc -triple=x86_64 %s -o - | FileCheck %s
+
+// CHECK: .section        .foo,"aM", at progbits,1
+// CHECK: .section        .bar,"aM", at progbits,4
+
+foo:
+.section .foo,"aM", at progbits,1
+
+.section .foo
+
+.pushsection .foo
+
+.pushsection .foo
+
+.section .bar,"aM", at progbits,4
+
+.section .bar
+
+.pushsection .bar,"aM", at progbits,4
+
+.pushsection .bar
Index: llvm/lib/MC/MCParser/ELFAsmParser.cpp
===================================================================
--- llvm/lib/MC/MCParser/ELFAsmParser.cpp
+++ llvm/lib/MC/MCParser/ELFAsmParser.cpp
@@ -652,10 +652,15 @@
       !(SectionName == ".eh_frame" && Type == ELF::SHT_PROGBITS))
     Error(loc, "changed section type for " + SectionName + ", expected: 0x" +
                    utohexstr(Section->getType()));
-  if (Section->getFlags() != Flags)
+  // Check that flags are used consistently. However, the GNU assembler permits
+  // to leave out in subsequent uses of the same sections; for compatibility,
+  // do likewise.
+  if ((Flags || Size) &&
+      Section->getFlags() != Flags)
     Error(loc, "changed section flags for " + SectionName + ", expected: 0x" +
                    utohexstr(Section->getFlags()));
-  if (Section->getEntrySize() != Size)
+  if ((Flags || Size) &&
+      Section->getEntrySize() != Size)
     Error(loc, "changed section entsize for " + SectionName +
                    ", expected: " + Twine(Section->getEntrySize()));
 


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