Bug 21038 – wchar and dchar string alignment should be 2 and 4, respectively

The result of wcslen can be too low when compiling with dmd 2.093. Consider the following two files: //////////////////// testabcd.d /////////////////// import core.stdc.stddef; import core.stdc.stdio; import core.stdc.wchar_; const(wchar_t)* name = "abcd"; void test() { size_t length = wcslen(name); printf("length: %zd\n", length); printf("data: \""); for(const(wchar_t)* s = name; *s; s++) printf("%c", *s); printf("\"\n"); } /////////////////////////////////////////////////// //////////////////// testxyzw.d /////////////////// import testabcd; void main() { test(); } /////////////////////////////////////////////////// Running it results in the following output: length: 3 data: "abcd" The correct length would be 4. When compiling with ldc it works as expected. The filenames are important. When testxyzw.d is renamed to testx.d it produces the expected output.

The string data is getting misaligned. wcslen assumes properly aligned data. testabcd.d can be reduced to this: ---- alias wchar_t = dchar; const(wchar_t)* name = "abcd"; void test() { assert((cast(size_t) name) % wchar_t.sizeof == 0); /* Fails. Should pass. */ } ----

For the program: alias wchar_t = dchar; const(wchar_t)* x = "xz"; const(wchar_t)* name = "abcd"; void test() { assert((cast(size_t) name) % wchar_t.sizeof == 0); /* Fails. Should pass. */ } the output generated is: Section 6 .rodata PROGBITS,ALLOC,SIZE=0x0030(48),OFFSET=0x0040,ALIGN=16 0040: 78 0 0 0 7a 0 0 0 0 0 0 0 61 0 0 0 x...z.......a... 0050: 62 0 0 0 63 0 0 0 64 0 0 0 0 0 0 0 b...c...d....... 0060: 4 10 0 0 0 0 0 0 74 65 73 74 0 0 0 0 ........test.... It's a surprise to me that a 4 byte element array is supposed to be aligned to 8 bytes. I'm not seeing where this is a requirement?

Oh, I see now. For: alias wchar_t = dchar; const(wchar)* x = "xz"; const(wchar_t)* name = "abcd"; void test() { assert((cast(size_t) name) % wchar_t.sizeof == 0); /* Fails. Should pass. */ } the result is: Section 6 .rodata PROGBITS,ALLOC,SIZE=0x0030(48),OFFSET=0x0040,ALIGN=16 0040: 78 0 7a 0 0 0 61 0 0 0 62 0 0 0 63 0 x.z...a...b...c. 0050: 0 0 64 0 0 0 0 0 0 0 0 0 0 0 0 0 ..d............. 0060: 4 10 0 0 0 0 0 0 74 65 73 74 0 0 0 0 ........test.... which is wrongly aligned on a 2 byte boundary.

@WalterBright created dlang/dmd pull request #11528 "fix Issue 21038 - wchar and dchar string alignment should be 2 and 4,…" fixing this issue: - fix Issue 21038 - wchar and dchar string alignment should be 2 and 4, respectively https://github.com/dlang/dmd/pull/11528

dlang/dmd pull request #11528 "fix Issue 21038 - wchar and dchar string alignment should be 2 and 4,…" was merged into master: - 46994f578813b365050ce19ed0e0bcc132e7555b by Walter Bright: fix Issue 21038 - wchar and dchar string alignment should be 2 and 4, respectively https://github.com/dlang/dmd/pull/11528