On 1/15/2015 10:31 PM, Mike via D.gnu wrote:
On Thursday, 15 January 2015 at 12:01:05 UTC, Johannes Pfau wrote:
My best guess is that the strings are always placed in rodata, never in
separate sections. If you do write("x"), "x" is also in rodata, the
rodata section can't be removed. If you delete the write call there's
no reference to rodata and it's possible to remove the complete
section.
After some google-fu:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=192
Considering this was filed in 2000 I'd say it's not very likely to get
fixed soon :-(
So the best option is probably to get rid of this problem by patching
the compiler (@notypeinfo or -fnortti).
Here's a filthy sed hack to workaround this bug:
1) compile to assembly:
-----------------------------------------------
gdc -S -static -frelease -fno-emit-moduleinfo -nophoboslib -nostdlib
test.d --entry=main -ffunction-sections -fdata-sections
-Wl,--gc-sections -o test_temp.s
2) use sed to modify the assembly, putting each
string into its own section:
-----------------------------------------------
sed -e 's/^\(\.LC[0-9]*\)\(\:\)/\.section .rodata\1\n\1\2/g'
test_temp.s >test.s
3) compile the new assembly:
-----------------------------------------------
as test.s -o test.o
4) link:
-----------------------------------------------
ld test.o --entry=main --gc-sections -o test
5) verify:
-----------------------------------------------
objdump -s -j .rodata test
Contents of section .rodata:
400168 780a x.
size test
text data bss dec hex filename
338 0 0 338 152 test
6) execute:
------------------------------------------------
./test
x
Filthy, but cheap and effective. Fortunately it's all automated with
rdmd.
Mike
The problem with this is that the TypeInfo is used for a significant
number of things in the runtime, casting, allocation, and initialization
just to name a few. The type info for structures is already only
generated if it's allocated on the heap. I suspect though that I'm
probably just too tired right now to understand the intricacies of the
topic.
