[Bug 216275] New: Incorrect fts_pathlen in fts(3) man page

[bugzilla-daemon@xxxxxxxxxx]

https://bugzilla.kernel.org/show_bug.cgi?id=216275

            Bug ID: 216275
           Summary: Incorrect fts_pathlen in fts(3) man page
           Product: Documentation
           Version: unspecified
          Hardware: All
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P1
         Component: man-pages
          Assignee: documentation_man-pages@xxxxxxxxxxxxxxxxxxxx
          Reporter: philj56@xxxxxxxxx
        Regression: No

In the fts(3) man page, `fts_pathlen` is described as:
```
short           fts_pathlen;  /* strlen(fts_path) +
                                 strlen(fts_name) */
```

This was changed from `strlen(fts_path)` in the following commit:

<https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/commit/?id=10b6adae8ac6026b2bb69bc66d1e0fcb37c81696>

This is only correct when `fts_children()` is called, however. When
only `fts_read()` is used, the original `fts_pathlen = strlen(fts_path)`
is correct. This feels like a glibc bug to me, seeing as the original
behaviour is listed in the glibc source:

<https://sourceware.org/git/?p=glibc.git;a=blob;f=io/fts.h;h=e00575d154b1457ddd02a0ab67a4a5e3b10237c0;hb=HEAD#l98>

Assuming that glibc won't change, I think the man page should document
both behaviours.

The following program demonstrates the difference in behaviour:

```
#include <fts.h>
#include <pwd.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>

void test_fts_children(char *paths[])
{
        FTS* fts = fts_open(paths, FTS_LOGICAL, NULL);
        FTSENT* ftsent = fts_read(fts);
        FTSENT* child = fts_children(fts, 0);
        while (child != NULL) {
                printf("    %s %s %d %lu\n", child->fts_path, child->fts_name,
                                child->fts_pathlen, strlen(child->fts_path));
                child = child->fts_link;
        }
        fts_close(fts);
}

void test_fts_read(char *paths[])
{
        FTS* fts = fts_open(paths, FTS_LOGICAL, NULL);
        FTSENT* ftsent = fts_read(fts);
        for (; ftsent != NULL; ftsent = fts_read(fts)) {
                /* Don't go any deeper */
                if (ftsent->fts_level > 0 && (ftsent->fts_info & FTS_D)) {
                        fts_set(fts, ftsent, FTS_SKIP);
                        continue;
                }
                printf("    %s %s %d %lu\n", ftsent->fts_path,
ftsent->fts_name,
                                ftsent->fts_pathlen, strlen(ftsent->fts_path));
        }
        fts_close(fts);
}

int main() {
        struct passwd *pwd_entry = getpwuid(getuid());
        char *paths[] = {pwd_entry->pw_dir, NULL};
        printf("fts_children:\n");
        test_fts_children(paths);
        printf("\nfts_read:\n");
        test_fts_read(paths);
        return 0;
}
```

Sample output:
```
fts_children:
    /home/phil/ Templates 20 11
    /home/phil/ bin 14 11
    /home/phil/ Pictures 19 11
    /home/phil/ Public 17 11
    /home/phil/ Videos 17 11
    /home/phil/ Downloads 20 11
    /home/phil/ Music 16 11
    /home/phil/ Desktop 18 11
    /home/phil/ Documents 20 11

fts_read:
    /home/phil phil 10 10
    /home/phil/Templates Templates 20 20
    /home/phil/bin bin 14 14
    /home/phil/Pictures Pictures 19 19
    /home/phil/Public Public 17 17
    /home/phil/Videos Videos 17 17
    /home/phil/Downloads Downloads 20 20
    /home/phil/Music Music 16 16
    /home/phil/Desktop Desktop 18 18
    /home/phil/Documents Documents 20 20
    /home/phil phil 10 10
```

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