commit c01c62c76c60a5a5da0496e41faae907944c92dd
author Tobias Burnus <tobias@codesourcery.com> Tue Nov 30 14:33:48 2021 +0000
committer Hafiz Abid Qadeer <abidh@codesourcery.com> Tue Nov 30 14:45:26 2021 +0000
tree 3e62d0d86ca81fcd1b176a9eccd19fed3c1b940e
parent 6e2aecd759dc3f8bf664323388365ac234271e9b

[MC][ELF] Fix accepting abbreviated form with Type change

Follow up to D92052 and D94072, exposed due to D107707

Many assemblers to permit that only the first .section contains all
the attributes like '.lds_bss,"w",@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 make it much more likely to hit
that issue. That's fixed by this commit.

Reviewed By: MaskRay

Differential Revision: https://reviews.llvm.org/D114717

llvm/lib/MC/MCParser/ELFAsmParser.cpp

diff --git a/llvm/lib/MC/MCParser/ELFAsmParser.cpp b/llvm/lib/MC/MCParser/ELFAsmParser.cpp
index ddc41d0..e95019c1 100644
--- a/llvm/lib/MC/MCParser/ELFAsmParser.cpp
+++ b/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()));

llvm/test/MC/ELF/section-omitted-attributes.s

diff --git a/llvm/test/MC/ELF/section-omitted-attributes.s b/llvm/test/MC/ELF/section-omitted-attributes.s
index 5f89cda..108ecd0 100644
--- a/llvm/test/MC/ELF/section-omitted-attributes.s
+++ b/llvm/test/MC/ELF/section-omitted-attributes.s
@@ -4,6 +4,7 @@
 
 # CHECK: .section        .foo,"aM",@progbits,1
 # CHECK: .section        .rodata.cst8,"aM",@progbits,8
+# CHECK: .section        .lds_bss,"w",@nobits
 
 .section .foo,"aM",@progbits,1
 
@@ -15,3 +16,7 @@
 .section .rodata.cst8,"aM",@progbits,8
 
 .section .rodata.cst8
+
+# Likewise for Type changes
+.section        .lds_bss,"w",@nobits
+.section        .lds_bss