diff options
| -rw-r--r-- | gdb/ChangeLog | 4 | ||||
| -rw-r--r-- | gdb/gdbtypes.h | 38 |
2 files changed, 27 insertions, 15 deletions
diff --git a/gdb/ChangeLog b/gdb/ChangeLog index 9b6a825db38..7be1ebd84a3 100644 --- a/gdb/ChangeLog +++ b/gdb/ChangeLog @@ -1,3 +1,7 @@ +2001-09-05 Jim Blandy <jimb@redhat.com> + + * gdbtypes.h (struct type): Doc fix. + 2001-09-04 Elena Zannoni <ezannoni@redhat.com> From Daniel Jacobowitz <drow@mvista.com> diff --git a/gdb/gdbtypes.h b/gdb/gdbtypes.h index 17f00ce70f5..1e9832c7e88 100644 --- a/gdb/gdbtypes.h +++ b/gdb/gdbtypes.h @@ -231,21 +231,29 @@ struct type char *tag_name; - /* Length of storage for a value of this type. This is of length - of the type as defined by the debug info and not the length of - the value that resides within the type. For instance, an - i386-ext floating-point value only occupies 80 bits of what is - typically a 12 byte `long double'. Various places pass this to - memcpy and such, meaning it must be in units of HOST_CHAR_BIT. - Various other places expect they can calculate addresses by - adding it and such, meaning it must be in units of - TARGET_CHAR_BIT. For some DSP targets, in which HOST_CHAR_BIT - will (presumably) be 8 and TARGET_CHAR_BIT will be (say) 32, - this is a problem. One fix would be to make this field in bits - (requiring that it always be a multiple of HOST_CHAR_BIT and - TARGET_CHAR_BIT)--the other choice would be to make it - consistently in units of HOST_CHAR_BIT. */ - + /* Length of storage for a value of this type. This is what + sizeof(type) would return; use it for address arithmetic, + memory reads and writes, etc. This size includes padding. For + example, an i386 extended-precision floating point value really + only occupies ten bytes, but most ABI's declare its size to be + 12 bytes, to preserve alignment. A `struct type' representing + such a floating-point type would have a `length' value of 12, + even though the last two bytes are unused. + + There's a bit of a host/target mess here, if you're concerned + about machines whose bytes aren't eight bits long, or who don't + have byte-addressed memory. Various places pass this to memcpy + and such, meaning it must be in units of host bytes. Various + other places expect they can calculate addresses by adding it + and such, meaning it must be in units of target bytes. For + some DSP targets, in which HOST_CHAR_BIT will (presumably) be 8 + and TARGET_CHAR_BIT will be (say) 32, this is a problem. + + One fix would be to make this field in bits (requiring that it + always be a multiple of HOST_CHAR_BIT and TARGET_CHAR_BIT) --- + the other choice would be to make it consistently in units of + HOST_CHAR_BIT. However, this would still fail to address + machines based on a ternary or decimal representation. */ unsigned length; /* FIXME, these should probably be restricted to a Fortran-specific |