[PATCH] D114717: [MC][ELF] Fix accepting abbreviated form with Type change

[Tobias Burnus via Phabricator via llvm-commits]

burnus created this revision.
burnus added reviewers: jhenderson, MaskRay.
Herald added subscribers: jdoerfert, hiraditya, emaste.
burnus requested review of this revision.
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Follow up to D92052 <https://reviews.llvm.org/D92052> and D94072 <https://reviews.llvm.org/D94072>, exposed due to D107707 <https://reviews.llvm.org/D107707>

Many assemblers to permit that only the first .section contains all
the attributes like '.lds_bss,"w", at nobits' and later section only
use the name ('.lds_bss') inheriting those attributes from the first
section.  I turned out that the case that Type changed was missed
when implementing it - and D107707 <https://reviews.llvm.org/D107707> make it much more likely to hit
that issue. That's fixed by this commit.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D114717

Files:
  llvm/lib/MC/MCParser/ELFAsmParser.cpp
  llvm/test/MC/ELF/section-omitted-attributes.s


Index: llvm/test/MC/ELF/section-omitted-attributes.s
===================================================================
--- llvm/test/MC/ELF/section-omitted-attributes.s
+++ llvm/test/MC/ELF/section-omitted-attributes.s
@@ -4,6 +4,7 @@
 
 # CHECK: .section        .foo,"aM", at progbits,1
 # CHECK: .section        .rodata.cst8,"aM", at progbits,8
+# CHECK: .section        .lds_bss,"w", at nobits
 
 .section .foo,"aM", at progbits,1
 
@@ -15,3 +16,7 @@
 .section .rodata.cst8,"aM", at progbits,8
 
 .section .rodata.cst8
+
+# Likewise for Type changes
+.section        .lds_bss,"w", at nobits
+.section        .lds_bss
Index: llvm/lib/MC/MCParser/ELFAsmParser.cpp
===================================================================
--- llvm/lib/MC/MCParser/ELFAsmParser.cpp
+++ llvm/lib/MC/MCParser/ELFAsmParser.cpp
@@ -676,14 +676,14 @@
       getContext().getELFSection(SectionName, Type, Flags, Size, GroupName,
                                  IsComdat, UniqueID, LinkedToSym);
   getStreamer().SwitchSection(Section, Subsection);
-  if (Section->getType() != Type &&
+  // 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 (!TypeName.empty() && Section->getType() != Type &&
       !allowSectionTypeMismatch(getContext().getTargetTriple(), SectionName,
                                 Type))
     Error(loc, "changed section type for " + SectionName + ", expected: 0x" +
                    utohexstr(Section->getType()));
-  // 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 ((extraFlags || Size || !TypeName.empty()) && Section->getFlags() != Flags)
     Error(loc, "changed section flags for " + SectionName + ", expected: 0x" +
                    utohexstr(Section->getFlags()));


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