cc does always create binary with debug_info, but I do not specified
-g
reddit / freebsd

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ImDoingInMyName · 2022-11-18 01:41

hello, folks.

does clang creates always binary with debug\_info on freebsd 13?

$> cat test.c

\#include "stdio.h"

int main(void)

{

        printf("Hello, world!\\n");

        return 0;

}

$>cc -o test test.c

$>file test

test: ELF 64-bit LSB executable, x86-64, version 1 (FreeBSD),
dynamically linked, interpreter /libexec/ld-elf.so.1, for FreeBSD
13.1, FreeBSD-style, **with debug\_info**, not stripped

$> strip -S test

$> file test

test: ELF 64-bit LSB executable, x86-64, version 1 (FreeBSD),
dynamically linked, interpreter /libexec/ld-elf.so.1, for FreeBSD
13.1, FreeBSD-style, not stripped

after strip, debug\_info has gone.

why is that?

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kevans91 · 2022-11-18 06:10

I suspect what you're seeing is an artifact from one of the other
objects that gets linked in. Note:

    root@ifrit:/tmp # cc --verbose -o test test.c
    FreeBSD clang version 14.0.5 (https://github.com/llvm/llvm-
project.git llvmorg-14.0.5-0-gc12386ae247c)
    Target: x86_64-unknown-freebsd14.0
    Thread model: posix
    InstalledDir: /usr/bin
     "/usr/bin/cc" -cc1 -triple x86_64-unknown-freebsd14.0 -emit-obj
-mrelax-all --mrelax-relocations -disable-free -clear-ast-before-
backend -disable-llvm-verifier -discard-value-names -main-file-name
test.c -mrelocation-model static -mframe-pointer=all -ffp-contract=on
-fno-rounding-math -mconstructor-aliases -funwind-tables=2 -target-cpu
x86-64 -tune-cpu generic -mllvm -treat-scalable-fixed-error-as-warning
-debugger-tuning=gdb -v -fcoverage-compilation-dir=/tmp -resource-dir
/usr/lib/clang/14.0.5 -fdebug-compilation-dir=/tmp -ferror-limit 19
-fgnuc-version=4.2.1 -fcolor-diagnostics -faddrsig
-D__GCC_HAVE_DWARF2_CFI_ASM=1 -o /tmp/test-3fefe8.o -x c test.c
    clang -cc1 version 14.0.5 based upon LLVM 14.0.5 default target
x86_64-unknown-freebsd14.0
    #include "..." search starts here:
    #include <...> search starts here:
     /usr/lib/clang/14.0.5/include
     /usr/include
    End of search list.
     "/usr/bin/ld" --eh-frame-hdr -dynamic-linker /libexec/ld-elf.so.1
--hash-style=both --enable-new-dtags -o test /usr/lib/crt1.o
/usr/lib/crti.o /usr/lib/crtbegin.o -L/usr/lib /tmp/test-3fefe8.o
-lgcc --as-needed -lgcc_s --no-as-needed -lc -lgcc --as-needed -lgcc_s
--no-as-needed /usr/lib/crtend.o /usr/lib/crtn.o

Specifically:

    /usr/lib/crt1.o /usr/lib/crti.o /usr/lib/crtbegin.o ...
/usr/lib/crtend.o /usr/lib/crtn.o
    ...

Each of these has their own .debug\_info. Finally, let's try another
experiment:

    root@ifrit:/tmp # cc -c -o test.o test.c
    root@ifrit:/tmp # readelf -a test.o | grep -i debug
    # No output
    root@ifrit:/tmp # cc -g -c -o test.o test.c
    root@ifrit:/tmp # readelf -a test.o | grep -i debug
      [ 5] .debug_abbrev     PROGBITS         0000000000000000
0000007a
      [ 6] .debug_info       PROGBITS         0000000000000000
000000b0
      [ 7] .rela.debug_info  RELA             0000000000000000
00000360
      [ 8] .debug_str        PROGBITS         0000000000000000
000000fb
      [13] .debug_line       PROGBITS         0000000000000000
00000218
      [14] .rela.debug_line  RELA             0000000000000000
00000450
    Relocation section with addend (.rela.debug_info):
    000000000006 00040000000a R_X86_64_32         0000000000000000
.debug_abbrev + 0
    00000000000c 00050000000a R_X86_64_32         0000000000000000
.debug_str + 0
    000000000012 00050000000a R_X86_64_32         0000000000000000
.debug_str + 67
    000000000016 00060000000a R_X86_64_32         0000000000000000
.debug_line + 0
    00000000001a 00050000000a R_X86_64_32         0000000000000000
.debug_str + 6e
    000000000039 00050000000a R_X86_64_32         0000000000000000
.debug_str + 73
    000000000044 00050000000a R_X86_64_32         0000000000000000
.debug_str + 78
    Relocation section with addend (.rela.debug_line):

Our initial theory seems to hold up-

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[deleted] · 2022-11-18 07:26

[deleted]

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ImDoingInMyName · 2022-11-18 07:27

Great!   Thank you.