Description

The error is a signedness comparison issue in format_and_print_line() used by wget’s --version to print information such as the flags used to the compiler and linker when wget was built.

Relevant code from src/main.c:

int remaining_chars;
...
token = strtok (line_dup, " ");
while (token != NULL)
  {
    /* If however a token is much larger than the maximum
       line length, all bets are off and we simply print the
       token on the next line. */
    if (remaining_chars <= strlen (token))
      {
        if (printf ("\n%*c", TABULATION, ' ') < 0)
          return -1;
        remaining_chars = line_length - TABULATION;
      }
    if (printf ("%s ", token) < 0)
      return -1;
    remaining_chars -= strlen (token) + 1;  /* account for " " */
    token = strtok (NULL, " ");
  }

Where if remaining_chars goes negative the comparison remaining_chars <= strlen (token) erroneously returns true, causing all remaining tokens to be printed on the same line instead of being wrapped.

When the printed string contains a token longer than the wrapping width (line_length - TABULATION in the above) remaining_chars will go negative and trigger this issue. Humorously we encountered this issue only because of a very long flag used by our research compiler that took a path name as an argument.

Status

This issue has been reported [1], and is now fixed upstream [2] thanks to the wget developers working with me on the issue. While touching that code, also prettified wget’s --version` output in general (see below), and scored my first (minor) entry on a GNU tool’s ChangeLog. Woo!

Example

Before:

GNU Wget 1.14.74-8bf9-dirty built on linux-gnu.

+digest +https +ipv6 +iri +large-file +nls +ntlm +opie +ssl/gnutls

Wgetrc:
    /usr/local/etc/wgetrc (system)
Locale: /usr/local/share/locale
Compile: gcc -DHAVE_CONFIG_H -DSYSTEM_WGETRC="/usr/local/etc/wgetrc"
    -DLOCALEDIR="/usr/local/share/locale" -I. -I../lib -I../lib
    -DUNIMPORTANT_TEXT_TO_CREATE_VERY_LONG_TOKEN_IN_FLAG_STRING=123456789 -O2 -g
Link: gcc
    -DUNIMPORTANT_TEXT_TO_CREATE_VERY_LONG_TOKEN_IN_FLAG_STRING=123456789 -O2 -g -lnettle -lgnutls -lgcrypt -lgpg-error -lz -lz -lidn -luuid -lpcre ftp-opie.o gnutls.o http-ntlm.o ../lib/libgnu.a

After:

GNU Wget 1.14.74-8bf9-dirty built on linux-gnu.

+digest +https +ipv6 +iri +large-file +nls +ntlm +opie +ssl/gnutls

Wgetrc:
    /usr/local/etc/wgetrc (system)
Locale:
    /usr/local/share/locale
Compile:
    gcc -DHAVE_CONFIG_H -DSYSTEM_WGETRC="/usr/local/etc/wgetrc"
    -DLOCALEDIR="/usr/local/share/locale" -I. -I../lib -I../lib
    -DUNIMPORTANT_TEXT_TO_CREATE_VERY_LONG_TOKEN_IN_FLAG_STRING=123456789
    -O2 -g
Link:
    gcc
    -DUNIMPORTANT_TEXT_TO_CREATE_VERY_LONG_TOKEN_IN_FLAG_STRING=123456789
    -O2 -g -lnettle -lgnutls -lgcrypt -lgpg-error -lz -lz -lidn -luuid
    -lpcre ftp-opie.o gnutls.o http-ntlm.o ../lib/libgnu.a

References: