* Re: -fno-rtti
[not found] <20000313103358.C25605@neel>
@ 2000-03-13 11:20 ` llewelly
2000-04-01 0:00 ` -fno-rtti llewelly
0 siblings, 1 reply; 2+ messages in thread
From: llewelly @ 2000-03-13 11:20 UTC (permalink / raw)
To: Neelakanth Nadgir; +Cc: gcc-help
On Mon, 13 Mar 2000, Neelakanth Nadgir wrote:
>
> Hi,
> a quick question,
I believe gcc@gcc.gnu.org is for gcc developer
concerns; gcc-help@gcc.gnu.org is more apropriate for this question.
> If a code uses RTTI, can it be compiled with -fno-rtti ?
No. RTTI requires type_info nodes, which it uses to identify types at
runtime. For example, dynamic_cast<> works by comparing type_info nodes.
If you compile code which uses dynamic_cast<> or typeid with -fno-rtti,
g++ will generate an error.
>
> Why is it that for some codes -fno-rtti decreases codesize by as
> much as 5x?
Every type in a C++ program needs a type_info node. C++ programs often
contain many, many types. Thus the size increase.
However, in my experience, I do not think I have ever seen 5x
increase; 15-30% (1.15x to 1.3x) is more common.
[snip]
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: -fno-rtti
2000-03-13 11:20 ` -fno-rtti llewelly
@ 2000-04-01 0:00 ` llewelly
0 siblings, 0 replies; 2+ messages in thread
From: llewelly @ 2000-04-01 0:00 UTC (permalink / raw)
To: Neelakanth Nadgir; +Cc: gcc-help
On Mon, 13 Mar 2000, Neelakanth Nadgir wrote:
>
> Hi,
> a quick question,
I believe gcc@gcc.gnu.org is for gcc developer
concerns; gcc-help@gcc.gnu.org is more apropriate for this question.
> If a code uses RTTI, can it be compiled with -fno-rtti ?
No. RTTI requires type_info nodes, which it uses to identify types at
runtime. For example, dynamic_cast<> works by comparing type_info nodes.
If you compile code which uses dynamic_cast<> or typeid with -fno-rtti,
g++ will generate an error.
>
> Why is it that for some codes -fno-rtti decreases codesize by as
> much as 5x?
Every type in a C++ program needs a type_info node. C++ programs often
contain many, many types. Thus the size increase.
However, in my experience, I do not think I have ever seen 5x
increase; 15-30% (1.15x to 1.3x) is more common.
[snip]
^ permalink raw reply [flat|nested] 2+ messages in thread
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2000-03-13 11:20 ` -fno-rtti llewelly
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