[PATCH 3/5] gdb: allow duplicate enumerators in flag enums
Simon Marchi
simon.marchi@efficios.com
Thu Feb 13 20:30:00 GMT 2020
I have come across some uses cases where it would be desirable to treat
an enum that has duplicate values as a "flag enum". For example, this
one here [1]:
enum membarrier_cmd {
MEMBARRIER_CMD_QUERY = 0,
MEMBARRIER_CMD_GLOBAL = (1 << 0),
MEMBARRIER_CMD_GLOBAL_EXPEDITED = (1 << 1),
MEMBARRIER_CMD_REGISTER_GLOBAL_EXPEDITED = (1 << 2),
MEMBARRIER_CMD_PRIVATE_EXPEDITED = (1 << 3),
MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED = (1 << 4),
MEMBARRIER_CMD_PRIVATE_EXPEDITED_SYNC_CORE = (1 << 5),
MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED_SYNC_CORE = (1 << 6),
/* Alias for header backward compatibility. */
MEMBARRIER_CMD_SHARED = MEMBARRIER_CMD_GLOBAL,
};
The last enumerator is kept for backwards compatibility. Without this
patch, this enumeration wouldn't be considered a flag enum, because two
enumerators collide. With this patch, it would be considered a flag
enum, and the value 3 would be printed as:
MEMBARRIER_CMD_GLOBAL | MEMBARRIER_CMD_GLOBAL_EXPEDITED
Although if people prefer, we could display both MEMBARRIER_CMD_GLOBAL
and MEMBARRIER_CMD_SHARED in the result. It wouldn't be wrong, and
could perhaps be useful in case a bit may have multiple meanings
(depending on some other bit value).
[1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/include/uapi/linux/membarrier.h?id=0bf999f9c5e74c7ecf9dafb527146601e5c848b9#n125
---
gdb/dwarf2/read.c | 5 -----
gdb/testsuite/gdb.base/printcmds.c | 7 ++++---
2 files changed, 4 insertions(+), 8 deletions(-)
diff --git a/gdb/dwarf2/read.c b/gdb/dwarf2/read.c
index b866cc2d5747..5c34667ef36d 100644
--- a/gdb/dwarf2/read.c
+++ b/gdb/dwarf2/read.c
@@ -15495,7 +15495,6 @@ update_enumeration_type_from_children (struct die_info *die,
struct die_info *child_die;
int unsigned_enum = 1;
int flag_enum = 1;
- ULONGEST mask = 0;
auto_obstack obstack;
@@ -15533,10 +15532,6 @@ update_enumeration_type_from_children (struct die_info *die,
if (nbits != 0 && nbits && nbits != 1)
flag_enum = 0;
- else if ((mask & value) != 0)
- flag_enum = 0;
- else
- mask |= value;
}
/* If we already know that the enum type is neither unsigned, nor
diff --git a/gdb/testsuite/gdb.base/printcmds.c b/gdb/testsuite/gdb.base/printcmds.c
index f0b4fa4b86b1..81d2efe1a037 100644
--- a/gdb/testsuite/gdb.base/printcmds.c
+++ b/gdb/testsuite/gdb.base/printcmds.c
@@ -99,9 +99,10 @@ volatile enum some_volatile_enum some_volatile_enum = enumvolval1;
/* An enum considered as a "flag enum". */
enum flag_enum
{
- FE_NONE = 0x00,
- FE_ONE = 0x01,
- FE_TWO = 0x02,
+ FE_NONE = 0x00,
+ FE_ONE = 0x01,
+ FE_TWO = 0x02,
+ FE_TWO_LEGACY = 0x02,
};
enum flag_enum three = FE_ONE | FE_TWO;
--
2.25.0
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