[PATCH] D74309: [DebugInfo] Add check for zero debug line opcode_base

[David Blaikie via Phabricator via llvm-commits]

dblaikie added a comment.

Please add an assembly+dumper test or a unit test, not both, in this instance (& usually preferred in general - there are some cases where it's worthwhile having both).



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Comment at: llvm/lib/DebugInfo/DWARF/DWARFDebugLine.cpp:358-367
+  if (OpcodeBase == 0) {
+    // If the opcode base is 0, we cannot read the standard opcode lengths (of
+    // which there are supposed to be one fewer than the opcode base). Assume
+    // there are no standard opcodes and continue parsing.
+    RecoverableErrorCallback(createStringError(
+        errc::invalid_argument,
+        "parsing line table prologue at offset 0x%8.8" PRIx64
----------------
I don't /think/ this merits a warning. It seems to be unexceptionally DWARF conformant to have an opcode base of 0:

"Opcode base is typically one greater than the highest-numbered standard opcode defined for the specified version of the line number information (12 in DWARF Versions 3, 4 and 5, and 9 in Version 2). If opcode_base is less than the typical value, then standard opcode numbers greater than or equal to the opcode base are not used in the line number table of this unit (and the codes are treated as special opcodes)."




================
Comment at: llvm/test/tools/llvm-dwarfdump/X86/Inputs/debug_line_malformed.s:398-411
+.asciz "dir1"           # Include table
+.asciz "dir2"
+.byte   0
+.asciz "file1"          # File table
+.byte   0, 0, 0
+.asciz "file2"
+.byte   1, 2, 3
----------------
Since this is only testing opcode base - perhaps it could have fewer/shorter details here? One directory and one file, perhaps? (I guess you've added/plan to add sufficient validation that it wouldn't be acceptable (would produce other warnings that would complicate the test case) to have zero files/directories and a line table program that's only a DW_LNE_end_sequence?)


Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D74309/new/

https://reviews.llvm.org/D74309