Fix GH-13932: Attempt to fix mbstring on windows build (msvc).

Build failure due to lack of VLA support in older compiler versions.

Fix infinite loop in mb_encode_mimeheader

Fix segfault caused by use of 'pass' encoding when mbstring converts multipart form POST data

When mbstring.encoding_translation=1, and PHP receives an (RFC1867)
form-based file upload,

Fix segfault caused by use of 'pass' encoding when mbstring converts multipart form POST data

When mbstring.encoding_translation=1, and PHP receives an (RFC1867)
form-based file upload, and the Content-Disposition HTTP header contains
a filename for the uploaded file, PHP will internally invoke mbstring
code to 1) try to auto-detect the text encoding of the filename, and if
that succeeds, 2) convert the filename to internal text encoding.

In such cases, the candidate text encodings which are considered during
"auto-detection" are those listed in the INI parameter
mbstring.http_input. Further, mbstring.http_input is one of the few
contexts where mbstring allows the magic string "pass" to appear in
place of an actual text encoding name.

Before mbstring's encoding auto-detection function was reimplemented,
the old implementation would never return "pass", even if "pass" was the
only candidate it was given to choose from. It is not clear if this was
intended by the original developers or not. This behavior was the result
of some rather subtle details of the implementation.

After mbstring's auto-detection function was reimplemented, if the new
implementation was given only one candidate to choose, and it was not
running in 'strict' mode, it would always return that candidate, even
if the candidate was the non-encoding "pass".

The upshot of all of this: Previously, if
mbstring.encoding_translation=1 and mbstring.http_input=pass, encoding
conversion of RFC1867 filenames would never be attempted. But after
the reimplementation, encoding 'conversion' would occur (uselessly).

Further, in December 2022, I reimplemented the relevant bit of
encoding conversion code. When doing this, I never bothered to
implement encoding/decoding routines for the non-encoding "pass",
because I thought that they would never be used. Well, in the one case
described above, those routines *would* have been used, had they
actually existed. Because they didn't exist, we get a nice NULL pointer
dereference and ensuing segfault instead.

Instead of 'fixing' this by adding encoding/decoding routines for the
non-encoding "pass", I have modified the function which the RFC1867
form-handling code invokes to auto-detect input encoding. This function
will never return "pass" now, just like the previous implementation.

Thanks to the GitHub user 'tstangner' for reporting this bug.

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Do not allow zend.script_encoding to be set to 'pass'

When investigating another bug reported by GitHub user 'tstangner',
I discovered that PHP segfaults when the INI parameter
zend.

Do not allow zend.script_encoding to be set to 'pass'

When investigating another bug reported by GitHub user 'tstangner',
I discovered that PHP segfaults when the INI parameter
zend.script_encoding is set to "pass". This bug dates back to
December 2022 (caused by yours truly in 953864661a).

If any PHP users in the wild were actually setting zend.script_encoding
to "pass" (which would be an utterly useless thing to do), I expect that
someone would have filed a bug report by now. The absence of such bug
reports is evidence that nobody is doing this.

Hence, it seems that the best fix is simply to disallow "pass" as a
choice for zend.script_encoding. The internal function
'php_mb_zend_encoding_list_parser' which I am modifying to accomplish
this has no other in-tree callers, aside from the 'exif' extension.
Further, exif only calls the function with a few hard-coded values, and
none of them are the string "pass", so this change will not have any
impact on exif.

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Fix bug in mb_get_substr_slow (sometimes outputs wrong number of characters)

Thanks to Maurício Fauth for finding and reporting this bug.

The bug was introduced in October 2022. It

Fix bug in mb_get_substr_slow (sometimes outputs wrong number of characters)

Thanks to Maurício Fauth for finding and reporting this bug.

The bug was introduced in October 2022. It originally only affected
text encodings which do not have a fixed byte width per characters
and for which mbstring does not have an mblen_table. However, I recently
made another change to mbstring, such that mb_substr no longer relies
on the mblen_table even if one is available. Because of this change,
the bug earlier introduced in October 2022 now affected a greater
number of text encodings, including UTF-8.

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Character indices used by mb_strpos and mb_substr have same meaning, even on invalid strings

Starting many years ago, libmbfl included a 'mblen_table' for selected
text encodings. This t

Character indices used by mb_strpos and mb_substr have same meaning, even on invalid strings

Starting many years ago, libmbfl included a 'mblen_table' for selected
text encodings. This table allows looking up the byte length of a
(possibly multi-byte) character from the value of the first byte.
libmbfl uses these tables to optimize certain operations; if a
text-processing operation can be performed using an mblen_table,
it may not be necessary to decode the text to codepoints. Since
libmbfl's decoding filters are generally slow, this improves
performance.

Since mbstring is (or was) based on libmbfl, it has always used
these mblen_tables to implement some functions. This design has a
significant downside. Let me explain:

While some mbstring functions are implemented by converting input text
to codepoints and operating on the codepoints, others operate directly
on the original input bytes (using an mblen_table to identify character
boundaries). Both of these implementation styles, if correctly coded,
yield equivalent results on valid strings. However, on strings which
contain encoding errors, the results are often different.

When decoding byte strings to codepoints using some text encoding,
mbstring uses the non-existent codepoint 0xFFFFFFFF to represent a
byte sequence which cannot be decoded. Then, when mbstring indexes into
the resulting sequence of codepoints, the index of any particular
character depends on the number of such 'error markers' which were
produced during the decoding process. In contrast, when an mblen_table
is used to split a byte sequence into characters, there is no question
of counting encoding errors; rather, table lookups into the mblen_table
are used to repeatedly 'bite off' some number of bytes (which are
treated as one 'character'). In the presence of encoding errors, these
two methods of mapping between byte indices and character indices are
inherently different and will rarely agree.

(For completeness, it must be said that some internal mbstring code
which operates only on UTF-8 text uses a third method for mapping
between byte indices and character indices, that is: counting
non-continuation UTF-8 bytes, which are all bytes whose binary
representation is NOT like 0b10xxxxxx. This method happens to agree with
the method which involves decoding the input text to codepoints and then
counting the codepoints.)

I have been aware of this issue for years, but only recently became
aware that in the case of mb_strstr, mb_strpos, and mb_substr,
this issue can cause seriously unintuitive behavior (and even security
vulnerabilities). This was reported by Stefan Schiller.

Stefan Schiller shared the following example for mb_strstr:

var_dump(mb_strstr("\xf0start", "start", false, "UTF-8"));
// string(2) "rt"

Similarly, when mb_strpos and mb_substr are used to identify and
extract a substring from a string with encoding errors, Stefan Schiller
pointed out that the extracted portion may be completely different than
desired. This is because (for UTF-8 strings) mb_strpos works by counting
non-continuation bytes, but mb_substr uses an mblen_table.

Since some mbstring functions *cannot* be implemented using an
mblen_table, as long as mblen_tables are used, similar inconsistencies
cannot be totally avoided. But the mblen_tables are critical to
mbstring's performance. Or are they? Benchmarking mb_substr on various
UTF-8, SJIS, and EUC-JP strings revealed something interesting.
On all SJIS and EUC-JP test cases, mb_substr was slightly faster when
the mblen_table based code was deleted. For some UTF-8 test cases, the
mblen_table-based code was a tiny bit faster, while for others the
fallback code was a touch faster; in no case was the difference
significant.

Therefore, the simple fix is to delete the mblen_table-based
implementation of mb_substr.

Aside from making the function behave consistently with other mbstring
functions on invalid strings, there is ONE case where behavior is now
different on valid strings: that is, on SJIS-Mac (MacJapanese) strings
which contain any of the following code units:

0x85AB-0x85AD, 0x85BF, 0x85C0, 0x85C1, 0x8645, 0x864B, 0x865D, 0x869E,
0x86CE, 0x86D3-0x86D5, 0x86D6, 0x8971, 0x8792, 0x879D, 0x87FB, 0x87FC,
0xEB41, 0xEB42, 0xEB50, 0xEB5B, 0xEB5D, 0xEB60-0xEB6E, and all from
0xEB81 and above.

All of these SJIS-Mac code units share the (very unusual) property that
they do not correspond to any one Unicode codepoint. When converting
from SJIS-Mac to Unicode, these must be converted to 2, 3, 4, or 5
codepoints each.

The previous, mblen_table-based implementation of mb_substr would treat
all of these SJIS-Mac byte sequences as 'one character'. Now, they are
treated as multiple characters (one for each of the Unicode codepoints
which they decode to). The new behavior is more consistent with other
mbstring functions.

I don't know if SJIS-Mac users will like this change or not (probably
most will never notice), but the BC break is justified by the very
real security impact of the previous, inconsistent behavior.

Finally, I should comment on whether similar changes are needed
elsewhere. The remaining functions which use an mblen_table are:
mb_str_split, mb_strcut, and various search functions (such as
mb_strpos). The search functions are only affected now when they
receive a positive 'offset' parameter specifying where to start
searching from.

The search functions should definitely be fixed so they do not use
an mblen_table to implement the 'offset' parameter. I am not convinced
that there is any good reason to change mb_str_split and mb_strcut.

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Fix GH-11992: utf_encodings.phpt fails on Windows 32-bit

Similar bug as before in #10776, but now in other code.

Closes GH-12726.

Fix infinite loop when mb_detect_encoding is used on UTF-8 BOM

This bug was introduced in cb840799b4.

Thanks to Ignace Nyamagana Butera for discovering this bug and
to Sebastian

Fix infinite loop when mb_detect_encoding is used on UTF-8 BOM

This bug was introduced in cb840799b4.

Thanks to Ignace Nyamagana Butera for discovering this bug and
to Sebastian Bergmann for doing an initial investigation and opening
a bug ticket.

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fix mbstring.c -Wsingle-bit-bitfield-constant-conversion (#12327)

These were both local variables, so there isn't much value in using
bitfields in the first place.

Fix uaf of MBSTRG(all_encodings_list)

We need to remove the value from the GC buffer before freeing it. Otherwise
shutdown will uaf when running the gc. Do that by switching from
zen

Fix uaf of MBSTRG(all_encodings_list)

We need to remove the value from the GC buffer before freeing it. Otherwise
shutdown will uaf when running the gc. Do that by switching from
zend_hash_destroy to zend_array_destroy, which should also be faster for freeing
members due to inlining of i_zval_ptr_dtor.

Closes GH-11822

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Deprecate passing a negative width to mb_strimwidth()

Fix GH-11567: mb_str_pad causes access violation

When not providing a pad string, *and* not having other defaulted
arguments, the function would crash on a NULL pad zend_string*.
Des

Fix GH-11567: mb_str_pad causes access violation

When not providing a pad string, *and* not having other defaulted
arguments, the function would crash on a NULL pad zend_string*.
Despite testing with an empty pad string, the issue wasn't found because
when using named arguments the pad string *is* filled in.

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Fix GH-11514: PHP 8.3 build fails with --enable-mbstring enabled

I tweaked the #if check such that the workaround only applies on GCC
versions older than 8.0.
I tested this with GCC

Fix GH-11514: PHP 8.3 build fails with --enable-mbstring enabled

I tweaked the #if check such that the workaround only applies on GCC
versions older than 8.0.
I tested this with GCC 7.5, 8.4, 9.4, GCC 13.1.1, and Clang 10.0.

Closes GH-11516.

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mbstring count_demerits in reverse order (#11493)

This way we can avoid moving candidates that would be eliminated after.

[RFC] Implement mb_str_pad() (#11284)

Closes GH-10203.

Fix GH-11476: crash with count_demerits negative-size-param

Co-authored-by: Ilija Tovilo <ilija.tovilo@me.com>
Co-authored-by: Niels Dossche <7771979+nielsdos@users.noreply.github.com>

Remove unused variable err in mb_send_mail() (#11285)

Use pakutoma's encoding check functions for mb_detect_encoding even in non-strict mode

In 6fc8d014df, pakutoma added specialized validity checking functions
for some legacy text encoding

Use pakutoma's encoding check functions for mb_detect_encoding even in non-strict mode

In 6fc8d014df, pakutoma added specialized validity checking functions
for some legacy text encodings like ISO-2022-JP and UTF-7. These
check functions perform a more strict validity check than the encoding
conversion functions for the same text encodings. For example, the
check function for ISO-2022-JP verifies that the string ends in the
correct state required by the specification for ISO-2022-JP.

These check functions are already being used to make detection of text
encoding more accurate when 'strict' detection mode is enabled.

However, since the default is 'non-strict' detection (a bad API design
but we're stuck with it now), most users will not benefit from
pakutoma's work. I was previously reluctant to enable this new logic
for non-strict detection mode. My intention was to reduce the scope of
behavior changes, since almost *any* behavior change may affect *some*
user in a way we don't expect.

However, we definitely have users whose (production) code was broken
by the changes I made in 28b346bc06, and enabling pakutoma's check
functions for non-strict detection mode would un-break it. (See
GH-10192 as an example.) The added checks do also make sense.

In non-strict detection mode, we will not immediately reject candidate
encodings whose validity check function returns false; but they will
be much less likely to be selected. However, failure of the validity
check function is weighted less heavily than an encoding error detected
by the encoding conversion function.

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Take order of candidate encodings into account when guessing text encoding

The documentation for mb_detect_encoding says that this function
"Detects the most likely character encoding fo

Take order of candidate encodings into account when guessing text encoding

The documentation for mb_detect_encoding says that this function
"Detects the most likely character encoding for string `string` from an
ordered list of candidates".

Prior to 28b346bc06, mb_detect_encoding did not really attempt to
determine the "most likely" text encoding for the input string. It
would just return the first candidate encoding for which the string was
valid. In 28b346bc06, I amended this function so that it uses heuristics
to try to guess which candidate encoding is "most likely".

However, the caller did not have any way to indicate which candidate
text encoding(s) they consider to be more likely, in case the
heuristics applied are inconclusive. In the language of Bayesian
probability, there was no way for the caller to indicate their 'prior'
assignment of probabilities.

Further, the documentation for mb_detect_encoding also says that the
second parameter `encodings` is "a list of character encodings to try,
in order". The documentation clearly implies that the order of
the `encodings` argument should be significant.

Therefore, amend mb_detect_encoding so that while it still uses
heuristics to guess the most likely text encoding for the input string,
it favors those which are earlier in the list of candidate encodings.

One complication is that many callers of mb_detect_encoding use it
in this way:

mb_detect_encoding($string, mb_list_encodings());

In a majority of cases, this is bad code; mb_detect_encoding will both
be much slower and the results will be less reliable than if a smaller
list of candidates is used. However, since such code already exists and
people are using it in production, we should not unnecessarily break it.
The order of candidate encodings obviously does not express any prior
belief of which candidates are more likely in this case, and treating
it as if it did will degrade the accuracy of the result.

Since mb_list_encodings now returns a single, immutable array on each
call, we can avoid that problem by turning off the new behavior when
we receive the array of encodings returned by mb_list_encodings.
This implementation means that if the user does this:

$a = mb_list_encodings();
mb_detect_encoding($string, $a);

...then the order of candidate encodings will not be considered.
However, if the user explicitly initializes their own array of all
supported legacy text encodings, then the order *will* be considered.

The other functions which also follow this new behavior are:

• mb_convert_variables
• mb_convert_encoding (when multiple candidate input encodings are
listed)

Other places where "detection" (or really "guessing") of text encoding
may be performed include:

• mb_send_mail
• Zend engine, when determining the encoding of a PHP script
• mbstring processing of HTTP request contents, when http_input INI
parameter is set to a list

In these cases, the new logic based on order of candidate encodings
is *not* enabled. It *might* be logical to consider the order of
candidate encodings in some or all of these cases, but I'm not sure if
that is true, so it seems wiser to avoid more behavior changes than is
necessary. Further, ever since the new encoding detection heuristics
were implemented in 28b346bc06, we have not received any complaints of
user code being broken in these areas. So I am reluctant to "fix what
isn't broken".

Well, some might say that applying the new detection heuristics
to mb_send_mail, etc. in 28b346bc06 was "fixing what wasn't broken",
but (cough cough) I don't have any comment on that...

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Use shared, immutable array for return value of mb_list_encodings

This will allow us to easily check in other mbstring functions if the
list of all supported encodings, returned by mb_li

Use shared, immutable array for return value of mb_list_encodings

This will allow us to easily check in other mbstring functions if the
list of all supported encodings, returned by mb_list_encodings, is
passed in as input to another function.

Co-authored-by: Ilija Tovilo <ilija.tovilo@me.com>

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[skip ci] Fix various typos and grammar issues (#11143)

mb_parse_str, mb_http_input, and mb_convert_variables use fast text conversion code for automatic encoding detection

For mb_parse_str, when mbstring.http_input (INI parameter) is a list of

mb_parse_str, mb_http_input, and mb_convert_variables use fast text conversion code for automatic encoding detection

For mb_parse_str, when mbstring.http_input (INI parameter) is a list of
multiple possible text encodings (which is not the case by default),
this new implementation is about 25% faster.

When mbstring.http_input is a single value, then nothing is changed.
(No automatic encoding detection is done in that case.)

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Fix phpGH-10648: add check function pointer into mbfl_encoding

Previously, mbstring used the same logic for encoding validation as for
encoding conversion.

However, there are ca

Fix phpGH-10648: add check function pointer into mbfl_encoding

Previously, mbstring used the same logic for encoding validation as for
encoding conversion.

However, there are cases where we want to use different logic for validation
and conversion. For example, if a string ends up with missing input
required by the encoding, or if a character is input that is invalid
as an encoding but can be converted, the conversion should succeed and
the validation should fail.

To achieve this, a function pointer mb_check_fn has been added to
struct mbfl_encoding to implement the logic used for validation.
Also, added implementation of validation logic for UTF-7, UTF7-IMAP,
ISO-2022-JP and JIS.

(The same change has already been made to PHP 8.2 and 8.3; see
6fc8d014df. This commit is backporting the change to PHP 8.1.)

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Fix compile error in Windows CI job caused by 0779950768

In 6fc8d014df, pakutoma added some additional validation logic to
mb_detect_encoding. Since the implementation of mb_detect_encod

Fix compile error in Windows CI job caused by 0779950768

In 6fc8d014df, pakutoma added some additional validation logic to
mb_detect_encoding. Since the implementation of mb_detect_encoding
has changed significantly between PHP 8.2 and 8.3, when merging this
change down from PHP-8.2 into master, I had to port his code over to
the new implementation in master.

However, I did this in a wrong way. In merge commit 0779950768,
the ported code modifies a function argument (to mb_guess_encoding)
which is marked 'const'. In the Windows CI job, MS VC++ rightly
flags this as a compile error.

Adjust the code to accomplish the same thing, but without destructively
modifying 'const' arguments.

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Fix phpGH-10648: add check function pointer into mbfl_encoding

Previously, mbstring used the same logic for encoding validation as for
encoding conversion.

However, there are ca

Fix phpGH-10648: add check function pointer into mbfl_encoding

Previously, mbstring used the same logic for encoding validation as for
encoding conversion.

However, there are cases where we want to use different logic for validation
and conversion. For example, if a string ends up with missing input
required by the encoding, or if a character is input that is invalid
as an encoding but can be converted, the conversion should succeed and
the validation should fail.

To achieve this, a function pointer mb_check_fn has been added to
struct mbfl_encoding to implement the logic used for validation.
Also, added implementation of validation logic for UTF-7, UTF7-IMAP,
ISO-2022-JP and JIS.

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