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cf138b0c83
The example did not work because the null byte was not converted, and mbrtowc was called with a zero-length input string. This results in a (size_t) -2 return value, so the function always returns NULL. The size computation for the heap allocation of the result was incorrect because it did not deal with integer overflow. Error checking was missing, and the allocated memory was not freed on error paths. All error returns now set errno. (Note that there is an assumption that free does not clobber errno.) The slightly unportable comparision against (size_t) -2 to catch both (size_t) -1 and (size_t) -2 return values is gone as well. A null wide character needs to be stored in the result explicitly, to terminate it. The description in the manual is updated to deal with these finer points. The (size_t) -2 behavior (consuming the input bytes) matches what is specified in ISO C11.
54 lines
1.2 KiB
C
54 lines
1.2 KiB
C
#include <stdbool.h>
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#include <stdlib.h>
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#include <string.h>
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#include <wchar.h>
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/* Do not include the above headers in the example.
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*/
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wchar_t *
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mbstouwcs (const char *s)
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{
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/* Include the null terminator in the conversion. */
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size_t len = strlen (s) + 1;
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wchar_t *result = reallocarray (NULL, len, sizeof (wchar_t));
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if (result == NULL)
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return NULL;
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wchar_t *wcp = result;
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mbstate_t state;
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memset (&state, '\0', sizeof (state));
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while (true)
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{
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wchar_t wc;
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size_t nbytes = mbrtowc (&wc, s, len, &state);
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if (nbytes == 0)
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{
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/* Terminate the result string. */
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*wcp = L'\0';
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break;
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}
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else if (nbytes == (size_t) -2)
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{
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/* Truncated input string. */
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errno = EILSEQ;
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free (result);
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return NULL;
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}
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else if (nbytes == (size_t) -1)
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{
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/* Some other error (including EILSEQ). */
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free (result);
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return NULL;
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}
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else
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{
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/* A character was converted. */
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*wcp++ = towupper (wc);
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len -= nbytes;
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s += nbytes;
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}
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}
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return result;
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}
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