DWARF: Canonicalize tombstone values #4155
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kripken
commented
Sep 15, 2021
| @@ -336,7 +336,7 @@ Abbrev table for offset: 0x00000000 | |||
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| 0x0000011f: DW_TAG_lexical_block [22] * | |||
| DW_AT_low_pc [DW_FORM_addr] (0x0000000000000030) | |||
| DW_AT_high_pc [DW_FORM_data4] (0xffffffd0) | |||
| DW_AT_high_pc [DW_FORM_data4] (0x00000000) | |||
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This was a case of doing math with a tombstone.
kripken
commented
Sep 15, 2021
| @@ -141,7 +141,7 @@ Abbrev table for offset: 0x00000000 | |||
| DW_AT_high_pc [DW_FORM_data4] (0x00000000) | |||
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| 0x00000026: DW_TAG_subprogram [2] | |||
| DW_AT_low_pc [DW_FORM_addr] (0x0000000000000000) | |||
| DW_AT_low_pc [DW_FORM_addr] (0x00000000ffffffff) | |||
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This looks odd, but is what LLVM does, and LLVM's current dwarfdump (newer than the dumping code we are using here) will actually print (dead code) for this.
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This uses LLVM-style tombstone values in more places, and avoids
doing math on tombstone values incorrectly. This reduces a large
amount of dwarfdump verification errors that currently happen even on
hello world.
cc @pfaffe