NULL terminator on string included via AS's incbin directive

Question

I have some large string resources located in files that I include in my executable. I include them in the executable using the following. The *.S allows GCC to invoke as to produce the object file without any special processing.

    ;; ca_conf.S
    .section .rodata

    ;; OpenSSL's CA configuration
    .global ca_conf
    .type   ca_conf, @object
    .align  8
ca_conf:
ca_conf_start:
    .incbin "res/openssl-ca.cnf"
ca_conf_end:
    .byte 0

    ;; The string's size (if needed)
    .global ca_conf_size
    .type   ca_conf_size, @object
    .align  4
ca_conf_size:
    .int    ca_conf_end - ca_conf_start

I add a .byte 0 after including the string to ensure the string is NULL terminated. That allows me to use ca_conf as a C const char*, or {ca_conf,ca_conf_size} as a C++ string.

Will the assembler or linker rearrange things such that the NULL terminator could become separated from the string its terminating? Or will the assembler and linker always keep them together?

Answer 1

Because you're in assembler they will be kept together. One other point, because of the ALIGN 4 ca_conf_size may not be the length you are expecting, it can include upto 3 padding bytes.