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libiberty/buildargv: handle input consisting of only white space

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GDB makes use of the libiberty function buildargv for splitting the
inferior (program being debugged) argument string in the case where
the inferior is not being started under a shell.

I have recently been working to improve this area of GDB, and noticed
some unexpected behaviour to the libiberty function buildargv, when
the input is a string consisting only of white space.

What I observe is that if the input to buildargv is a string
containing only white space, then buildargv will return an argv list
containing a single empty argument, e.g.:

  char **argv = buildargv (" ");
  assert (*argv[0] == '\0');
  assert (argv[1] == NULL);

We get the same output from buildargv if the input is a single space,
or multiple spaces.  Other white space characters give the same
results.

This doesn't seem right to me, and in fact, there appears to be a work
around for this issue in expandargv where we have this code:

  /* If the file is empty or contains only whitespace, buildargv would
     return a single empty argument.  In this context we want no arguments,
     instead.  */
  if (only_whitespace (buffer))
    {
      file_argv = (char **) xmalloc (sizeof (char *));
      file_argv[0] = NULL;
    }
  else
    /* Parse the string.  */
    file_argv = buildargv (buffer);

I think that the correct behaviour in this situation is to return an
empty argv array, e.g.:

  char **argv = buildargv (" ");
  assert (argv[0] == NULL);

And it turns out that this is a trivial change to buildargv.  The diff
does look big, but this is because I've re-indented a block.  Check
with 'git diff -b' to see the minimal changes.  I've also removed the
work around from expandargv.

When testing this sort of thing I normally write the tests first, and
then fix the code.  In this case test-expandargv.c has sort-of been
used as a mechanism for testing the buildargv function (expandargv
does call buildargv most of the time), however, for this particular
issue the work around in expandargv (mentioned above) masked the
buildargv bug.

I did consider adding a new test-buildargv.c file, however, this would
have basically been a copy & paste of test-expandargv.c (with some
minor changes to call buildargv).  This would be fine now, but feels
like we would eventually end up with one file not being updated as
much as the other, and so test coverage would suffer.

Instead, I have added some explicit buildargv testing to the
test-expandargv.c file, this reuses the test input that is already
defined for expandargv.

Of course, once I removed the work around from expandargv then we now
do always call buildargv from expandargv, and so the bug I'm fixing
would impact both expandargv and buildargv, so maybe the new testing
is redundant?  I tend to think more testing is always better, so I've
left it in for now.

2024-07-16  Andrew Burgess  <aburgess@redhat.com>

libiberty/

	* argv.c (buildargv): Treat input of only whitespace as an empty
	argument list.
	(expandargv): Remove work around for intput that is only
	whitespace.
	* testsuite/test-expandargv.c: Add new tests 10, 11, and 12.
	Extend testing to call buildargv in more cases.
This commit is contained in:
Andrew Burgess 2024-02-10 11:22:13 +00:00
parent a87954610f
commit 5e1d530da8
2 changed files with 169 additions and 81 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

12
libiberty/argv.c
View File

@ -212,6 +212,8 @@ char **buildargv (const char *input)
argv[argc] = NULL;
}
/* Begin scanning arg */
if (*input != EOS)
{
arg = copybuf;
while (*input != EOS)
{
@ -277,6 +279,7 @@ char **buildargv (const char *input)
*arg = EOS;
argv[argc] = xstrdup (copybuf);
argc++;
}
argv[argc] = NULL;
consume_whitespace (&input);
@ -439,15 +442,6 @@ expandargv (int *argcp, char ***argvp)
}
/* Add a NUL terminator. */
buffer[len] = '\0';
/* If the file is empty or contains only whitespace, buildargv would
return a single empty argument. In this context we want no arguments,
instead. */
if (only_whitespace (buffer))
{
file_argv = (char **) xmalloc (sizeof (char *));
file_argv[0] = NULL;
}
else
/* Parse the string. */
file_argv = buildargv (buffer);
/* If *ARGVP is not already dynamically allocated, copy it. */

136
libiberty/testsuite/test-expandargv.c
View File

@ -176,6 +176,30 @@ const char *test_data[] = {
"\\t",
0,
/* Test 10 - Mixed white space characters. */
"\t \n \t ", /* Test 10 data */
ARGV0,
"@test-expandargv-10.lst",
0,
ARGV0,
0,
/* Test 11 - Single ' ' character. */
" ", /* Test 11 data */
ARGV0,
"@test-expandargv-11.lst",
0,
ARGV0,
0,
/* Test 12 - Multiple ' ' characters. */
" ", /* Test 12 data */
ARGV0,
"@test-expandargv-12.lst",
0,
ARGV0,
0,
0 /* Test done marker, don't remove. */
};
@ -265,6 +289,78 @@ erase_test (int test)
fatal_error (__LINE__, "Failed to erase test file.", errno);
}
/* compare_argv:
TEST is the current test number, and NAME is a short string to identify
which libibery function is being tested. ARGC_A and ARGV_A describe an
argument array, and this is compared to ARGC_B and ARGV_B, return 0 if
the two arrays match, otherwise return 1. */
static int
compare_argv (int test, const char *name, int argc_a, char *argv_a[],
int argc_b, char *argv_b[])
{
int failed = 0, k;
if (argc_a != argc_b)
{
printf ("FAIL: test-%s-%d. Argument count didn't match\n", name, test);
failed = 1;
}
/* Compare each of the argv's ... */
else
for (k = 0; k < argc_a; k++)
if (strcmp (argv_a[k], argv_b[k]) != 0)
{
printf ("FAIL: test-%s-%d. Arguments don't match.\n", name, test);
failed = 1;
break;
}
if (!failed)
printf ("PASS: test-%s-%d.\n", name, test);
return failed;
}
/* test_buildargv
Test the buildargv function from libiberty. TEST is the current test
number and TEST_INPUT is the string to pass to buildargv (after calling
run_replaces on it). ARGC_AFTER and ARGV_AFTER are the expected
results. Return 0 if the test passes, otherwise return 1. */
static int
test_buildargv (int test, const char * test_input, int argc_after,
char *argv_after[])
{
char * input, ** argv;
size_t len;
int argc, failed;
/* Generate RW copy of data for replaces */
len = strlen (test_input);
input = malloc (sizeof (char) * (len + 1));
if (input == NULL)
fatal_error (__LINE__, "Failed to malloc buildargv input buffer.", errno);
memcpy (input, test_input, sizeof (char) * (len + 1));
/* Run all possible replaces */
run_replaces (input);
/* Split INPUT into separate arguments. */
argv = buildargv (input);
/* Count the arguments we got back. */
argc = 0;
while (argv[argc])
++argc;
failed = compare_argv (test, "buildargv", argc_after, argv_after, argc, argv);
free (input);
freeargv (argv);
return failed;
}
/* run_tests:
Run expandargv
@ -276,12 +372,16 @@ run_tests (const char **test_data)
{
int argc_after, argc_before;
char ** argv_before, ** argv_after;
int i, j, k, fails, failed;
int i, j, k, fails;
const char * input_str;
i = j = fails = 0;
/* Loop over all the tests */
while (test_data[j])
{
/* Save original input in case we run a buildargv test. */
input_str = test_data[j];
/* Write test data */
writeout_test (i, test_data[j++]);
/* Copy argv before */
@ -305,29 +405,23 @@ run_tests (const char **test_data)
for (k = 0; k < argc_after; k++)
run_replaces (argv_after[k]);
/* If the test input is just a file to expand then we can also test
calling buildargv directly as the expected output is equivalent to
calling buildargv on the contents of the file.
The results of calling buildargv will not include the ARGV0 constant,
which is why we pass 'argc_after - 1' and 'argv_after + 1', this skips
over the ARGV0 in the expected results. */
if (argc_before == 2)
fails += test_buildargv (i, input_str, argc_after - 1, argv_after + 1);
else
printf ("SKIP: test-buildargv-%d. This test isn't for buildargv\n", i);
/* Run test: Expand arguments */
expandargv (&argc_before, &argv_before);
failed = 0;
/* Compare size first */
if (argc_before != argc_after)
{
printf ("FAIL: test-expandargv-%d. Number of arguments don't match.\n", i);
failed++;
}
/* Compare each of the argv's ... */
else
for (k = 0; k < argc_after; k++)
if (strcmp (argv_before[k], argv_after[k]) != 0)
{
printf ("FAIL: test-expandargv-%d. Arguments don't match.\n", i);
failed++;
}
if (!failed)
printf ("PASS: test-expandargv-%d.\n", i);
else
fails++;
fails += compare_argv (i, "expandargv", argc_before, argv_before,
argc_after, argv_after);
freeargv (argv_before);
freeargv (argv_after);