Compiler warning on create_library

[KristofferC]

In function ‘strncpy’,
    inlined from ‘set_depot_path’ at /home/kc/.julia/packages/PackageCompiler/0A6ug/src/julia_init.c:61:5:
/usr/include/x86_64-linux-gnu/bits/string_fortified.h:95:10: warning: ‘__builtin_strncpy’ specified bound depends on the length of the source argument [-Wstringop-overflow=]
   95 |   return __builtin___strncpy_chk (__dest, __src, __len,
      |          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   96 |       __glibc_objsize (__dest));
      |       ~~~~~~~~~~~~~~~~~~~~~~~~~
/home/kc/.julia/packages/PackageCompiler/0A6ug/src/julia_init.c: In function ‘set_depot_path’:
/home/kc/.julia/packages/PackageCompiler/0A6ug/src/julia_init.c:47:24: note: length computed here
   47 |     int root_dir_len = strlen(root_dir);
      |                        ^~~~~~~~~~~~~~~~

cc @kmsquire

[KristofferC]

This still seems to happen. Here is from a recent CI log:

In file included from /usr/include/string.h:495,
                 from /opt/hostedtoolcache/julia/1.6.3/x64/include/julia/dtypes.h:9,
                 from /opt/hostedtoolcache/julia/1.6.3/x64/include/julia/libsupport.h:10,
                 from /opt/hostedtoolcache/julia/1.6.3/x64/include/julia/julia.h:12,
                 from /home/runner/work/PackageCompiler.jl/PackageCompiler.jl/src/julia_init.c:13:
In function ‘strncpy’,
    inlined from ‘set_depot_path’ at /home/runner/work/PackageCompiler.jl/PackageCompiler.jl/src/julia_init.c:61:5:
/usr/include/x86_64-linux-gnu/bits/string_fortified.h:106:10: warning: ‘__builtin_strncpy’ specified bound depends on the length of the source argument [-Wstringop-overflow=]
  106 |   return __builtin___strncpy_chk (__dest, __src, __len, __bos (__dest));
      |          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/runner/work/PackageCompiler.jl/PackageCompiler.jl/src/julia_init.c: In function ‘set_depot_path’:
/home/runner/work/PackageCompiler.jl/PackageCompiler.jl/src/julia_init.c:47:24: note: length computed here
   47 |     int root_dir_len = strlen(root_dir);
      |                        ^~~~~~~~~~~~~~~~

https://github.com/JuliaLang/PackageCompiler.jl/runs/3720013049?check_suite_focus=true#step:4:1018

[KristofferC]

cc @kmsquire

[kmsquire]

Okay, I should have at least checked that my fix worked. ☹️ Sorry about that...

As far as I can ascertain, this isn't a problem in practice--we're allocating the buffer based on the size, and then using that value in strncpy. I'll try a few things to see if they silence the warning.

1. using strcpy. Also should be fine because of how we're allocating the buffer, but I'm guessing it'll cause a different compiler warning.
2. using a large, fixed sized buffer. Seems slightly wasteful, but it would probably silence the compiler warning. Unfortunately, it's hard to determine a good size to set this to, as the actual maximum path length depends on the operating system.

Any other ideas?

[KristofferC]

Seems fine to use strcpy here, or?

[kmsquire]

Okay, #561 actually fixes this (no warning in the logs).