Re: [Tinycc-devel] Minimizing libtcc memory use

[grischka]

On 08.03.2024 07:30, Eric Raible wrote:
> I guess that I just want the numbers to add up.
> Using your example:
>
> 1) -DMEM_DEBUG -DCONFIG_RUNMEM_RO=0
> 2) your test.c
> 3) but I added an early return to tcc_delete() to no-op it
>
> Running: valgrind tcc -nostdlib -vv -bench -run test.c
> produced:
>
> tcc version 0.9.28rc 2024-03-03 mob@9d2068c6* (AArch64 Linux)
> -> test.c
> ---------------------------------------------
> 0: .text            0x4ccb000  len 00020  align 1000
> 1: .data.ro         0x4ccb020  len 00004  align 0008
> 2: .data            0x4ccb028  len 00004  align 0008
> 2: .bss             0x4ccb030  len 00004  align 0008
> ---------------------------------------------
> protect         rwx 0x4ccb000  len 01000
> ---------------------------------------------
> # 3030 idents, 4 lines, 92 bytes
> # 0.463 s, 8 lines/s, 0.0 MB/s
> # text 32, data.rw <http://data.rw> 4, data.ro <http://data.ro> 4, bss 4 bytes
> # memory usage: 8192 to run, 649 symbols, 2901 other, 1639290 max (bytes)
> mem_cur_size=11742 (bytes)

> So tcc_print_stats() says 11742, but then displays values totaling 11786.

What 11786 ?

8192 + 649 + 2901 = 11742

> ==2188==
> ==2188== HEAP SUMMARY:
> ==2188==     in use at exit: 14,814 bytes in 32 blocks
>
> And valgrind reports 14814.  I have never seen valgrind wrong about this,
> and especially so b.c. my (luckily-correct) allocator reported 14814 as well.

There is nothing wrong here:  11742 + 32 blocks * 96 = 14814
Where 96 is the size of tcc's mem_debug extra header.

If you want to see the 11742 from valgrind then you just need to
run the same example with a normal tcc compiled without MEM_DEBUG.

Which makes sense I would think.

But when showing the example with MEM_DEBUG and -bench -vv  I
did not expect you to doubt the numbers in the first place.

Rather I just was trying to show how you could get some numbers
for your own real case instead.  Which as you suspect could be
minimized from 29kB down to 1-2 kB.  Most likely impossible but
if we had some numbers we could tell also why.

-- gr