Infinite recursion for utf8proc_decompose_char

[jvit]

In master branch, this code leads to infinite recursion and stack overflow:

int32_t codepoints[10];
int boundclass;
utf8proc_ssize_t decomp_result = utf8proc_decompose_char(64257, codepoints, 10, 
    (utf8proc_option_t)(UTF8PROC_COMPAT | UTF8PROC_DECOMPOSE), &boundclass);

call stack:

utf8proc_decompose_char(939, ...)
seqindex_write_char_decomposed(65535, ...)
utf8proc_decompose_char(933, ...)
seqindex_write_char_decomposed(9062, ...)
utf8proc_decompose_char(939, ...)
seqindex_write_char_decomposed(65535, ...)
utf8proc_decompose_char(933, ...)

In release-1.2, it works fine.

[jiahao]

The code for utf8proc_decompose_char with UTF8PROC_DECOMPOSE was most recently changed in eeebf70#diff-3008d7ea25bc1a2ce66a424402cae328R459 - could you git bisect and verify?

[jvit]

Yes, I verified with git bisect that this error was introduced in that commit.

[ivarne]

cc @benibela

[benibela]

Weird. It can never call seqindex_write_char_decomposed(65535, .. since it tests property->decomp_seqindex != UINT16_MAX before calling seqindex_write_char_decomposed(property->decomp_seqindex

What is UINT16_MAX?

[jvit]

UINT16_MAX is 65535.

I think the problem is in #define UINT16_MAX ~(utf8proc_uint16_t)0.

I don't know why, but 65535 != ~(utf8proc_uint16_t)0 evaluates to 1.

If I use #define UINT16_MAX 65535U everything works fine.

I am using Visual Studio 2015, Update 3. Maybe they have changed something in the compiler with the latest update?

[stevengj]

#define UINT16_MAX 65535U seems like an easy fix, can you make a PR?

[stevengj]

(Shouldn't we also be using UTF8PROC_UINT16_MAX etcetera since UINT16_MAX is defined in stdint.h?)

[eschnett]

C and C++ apply "integer promotion": Expressions that evaluate to an integer that is smaller than int are automatically converted to int. You are likely missing an explicit conversion to utf8proc_uint16_t after applying the ~ operator. The existing conversion is likely redundant because of integer promotion.

[stevengj]

Should be fixed by #84.