nob_get_file_type error check is dead code: nob_copy_directory_recursively aborts and nob_walk_dir returns true on unreadable paths

[NeikiDev]

nob_get_file_type() returns (Nob_File_Type)-1 to signal failure, but two callers check for that with if (type < 0). Nob_File_Type is an enum with only non-negative enumerators, so the compiler gives it an unsigned underlying type and the < 0 check is always false. The error is never caught.

• nob__walk_dir_opt_impl() (line 2122): the walk continues with an invalid file_type and nob_walk_dir() returns true for a path that could not be stat-ed.
• nob_copy_directory_recursively() (line 2328): execution falls through the switch to default: NOB_UNREACHABLE(...), which calls abort(). A missing or unreadable source directory crashes the whole program instead of returning false.

Both compile without warning under gcc -Wall -Wextra and clang -Wall -Wextra.

Repro

#define NOB_IMPLEMENTATION
#include "nob.h"

static bool walk_cb(Nob_Walk_Entry entry)
{
    (void) entry;
    return true;
}

int main(void)
{
    const char *missing = "this-path-does-not-exist";

    // nob_walk_dir() reports success on a path that could not be stat-ed
    bool walk_ok = nob_walk_dir(missing, walk_cb);
    nob_log(NOB_INFO, "nob_walk_dir returned %s", walk_ok ? "true" : "false");

    // nob_copy_directory_recursively() aborts instead of returning false
    bool copy_ok = nob_copy_directory_recursively(missing, "dst");
    nob_log(NOB_INFO, "nob_copy_directory_recursively returned %s", copy_ok ? "true" : "false");

    return 0;
}

$ cc -o poc poc.c && ./poc
[ERROR] Could not get stat of this-path-does-not-exist: No such file or directory
[INFO] nob_walk_dir returned true
[ERROR] Could not get stat of this-path-does-not-exist: No such file or directory
./nob.h:2372: UNREACHABLE: nob_copy_directory_recursively
$ echo $?
134

Reproduced on nob.h v3.10.0 with clang on macOS and gcc 14 on Linux (same output on both).

Potential fix

Compare against the sentinel value instead of < 0, which works whether the enum is signed or unsigned:

-    if (file_type < 0) nob_return_defer(false);
+    if (file_type == (Nob_File_Type)-1) nob_return_defer(false);

-    if (type < 0) return false;
+    if (type == (Nob_File_Type)-1) return false;

With that change nob_copy_directory_recursively() returns false on the missing path and nob_walk_dir() returns false, each after logging the stat error once.