I have a .i file which I have compiled but not linked using the SiFive risc-v compiler as follows:
../riscv64-unknown-elf-gcc-8.2.0-2019.05.3-x86_64-linux-ubuntu14/bin/riscv64-unknown-elf-gcc clock.i
However when I do a readelf -S on the compiled object file the .text section is 0 bytes:
Section Headers:
[Nr] Name Type Addr Off Size ES Flg Lk Inf Al
[ 0] NULL 00000000 000000 000000 00 0 0 0
[ 1] .text PROGBITS 00000000 000034 000000 00 AX 0 0 2
[ 2] .data PROGBITS 00000000 000034 000000 00 WA 0 0 1
[ 3] .bss NOBITS 00000000 000034 000000 00 WA 0 0 1
[ 4] .text.getTime PROGBITS 00000000 000034 00003a 00 AX 0 0 2
[ 5] .rela.text.ge RELA 00000000 000484 0000c0 0c I 18 4 4
[ 6] .text.timeGap PROGBITS 00000000 00006e 00002e 00 AX 0 0 2
[ 7] .rela.text.ti RELA 00000000 000544 000024 0c I 18 6 4
[ 8] .text.applyTO PROGBITS 00000000 00009c 000038 00 AX 0 0 2
[ 9] .rela.text.ap RELA 00000000 000568 0000c0 0c I 18 8 4
[10] .text.clearTO PROGBITS 00000000 0000d4 000038 00 AX 0 0 2
[11] .rela.text.cl RELA 00000000 000628 0000c0 0c I 18 10 4
[12] .rodata.getTi PROGBITS 00000000 00010c 00000c 01 AMS 0 0 4
[13] .rodata.__func__. PROGBITS 00000000 000118 00000c 00 A 0 0 4
[14] .rodata.__func__. PROGBITS 00000000 000124 00000c 00 A 0 0 4
[15] .rodata.__func__. PROGBITS 00000000 000130 00000c 00 A 0 0 4
[16] .comment PROGBITS 00000000 00013c 000029 01 MS 0 0 1
[17] .riscv.attributes LOPROC+0x3 00000000 000165 00001f 00 0 0 1
[18] .symtab SYMTAB 00000000 000184 000240 10 19 31 4
[19] .strtab STRTAB 00000000 0003c4 0000be 00 0 0 1
[20] .shstrtab STRTAB 00000000 0006e8 000100 00 0 0 1
If I do a size on the compiled object file I get a size of 264 bytes:
text data bss dec hex filename
264 0 0 264 108 clock.o
If I do an nm --print-size I get the following:
U __assert_func
00000000 0000000c r __func__.3507
00000000 0000000c r __func__.3518
00000000 0000000c r __func__.3522
0000000c t .L11
00000036 t .L12
00000034 t .L14
00000036 t .L18
00000034 t .L2
00000034 t .L20
00000032 t .L3
0000001e t .L8
00000000 r .LANCHOR0
00000000 r .LANCHOR1
00000000 r .LANCHOR2
00000000 r .LC0
00000004 r .LC1
00000000 00000038 T applyTO
00000000 00000038 T clearTO
00000000 0000003a T getTime
00000000 0000002e T timeGap
Which to me the size would be 0x38 + 0x38 + 0x3A + 0x2E = 0xD8 (216) bytes.
How can I calculate the size of a compiled object file?
Your object file is compiled with -ffunction-sections, a special flag which allocates each function to it's dedicated section. You can see individual .texts for each function in readelf's output:
[ 4] .text.getTime PROGBITS 00000000 000034 00003a 00 AX 0 0 2
...
[ 6] .text.timeGap PROGBITS 00000000 00006e 00002e 00 AX 0 0 2
...
To get full code size you'll need to sum sizes for each section starting with ".text". A Perl one-liner:
$ readelf ... | perl -ne 'if(/ \.text/) { s/^.*\] *//; $sz += hex((split(/ +/))[4]); print "$sz\n"; }' 0
58
104
160
216 <-- Full size