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

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@NeikiDev is already working on this.

Since Jul 25, 2026.

  • #263 by @NeikiDev — open

Assessment

Difficulty
2/5
Estimated time
1-3 hours
Newbie friendliness
88/100
Issue type
Bug
Clarity
Clearly specified
Activity status
Quiet
Tech stack
c
Domain
build-system, tooling

Research direction

Start in nob.h at nob__walk_dir_opt_impl() around line 2122 and nob_copy_directory_recursively() around line 2328, then inspect how nob_get_file_type() reports failure. Run the provided missing-path reproducer with GCC and Clang, and verify both callers return false after the stat error instead of continuing or aborting.

Written by the indexing model from the issue text.

Description

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.

Dominant language
C++
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