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From: Szabolcs Nagy <nsz@sourceware.org> To: glibc-cvs@sourceware.org Subject: [glibc/release/2.32/master] __vfscanf_internal: fix aliasing violation (bug 26690) Date: Thu, 21 Jan 2021 13:52:28 +0000 (GMT) [thread overview] Message-ID: <20210121135228.42AB93844013@sourceware.org> (raw) https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=082798622d888e2d1b39b0758a0a5f8530a558b2 commit 082798622d888e2d1b39b0758a0a5f8530a558b2 Author: Andreas Schwab <schwab@suse.de> Date: Thu Oct 1 13:59:13 2020 +0200 __vfscanf_internal: fix aliasing violation (bug 26690) As noted in <https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97264>, the cast in the call to the read_int function is an aliasing violation. Change the type of local variable f to a pointer to unsigned, which allows to eliminate most casts while only adding three new ones. (cherry picked from commit c0e9ddf59e73e21afe15fca4e94cf7b4b7359bf2) Diff: --- stdio-common/vfscanf-internal.c | 22 +++++++++++----------- 1 file changed, 11 insertions(+), 11 deletions(-) diff --git a/stdio-common/vfscanf-internal.c b/stdio-common/vfscanf-internal.c index 95b46dcbeb..3a323547f9 100644 --- a/stdio-common/vfscanf-internal.c +++ b/stdio-common/vfscanf-internal.c @@ -277,7 +277,7 @@ __vfscanf_internal (FILE *s, const char *format, va_list argptr, #endif { va_list arg; - const CHAR_T *f = format; + const UCHAR_T *f = (const UCHAR_T *) format; UCHAR_T fc; /* Current character of the format. */ WINT_T done = 0; /* Assignments done. */ size_t read_in = 0; /* Chars read in. */ @@ -415,10 +415,11 @@ __vfscanf_internal (FILE *s, const char *format, va_list argptr, #endif #ifndef COMPILE_WSCANF - if (!isascii ((unsigned char) *f)) + if (!isascii (*f)) { /* Non-ASCII, may be a multibyte. */ - int len = __mbrlen (f, strlen (f), &state); + int len = __mbrlen ((const char *) f, strlen ((const char *) f), + &state); if (len > 0) { do @@ -426,7 +427,7 @@ __vfscanf_internal (FILE *s, const char *format, va_list argptr, c = inchar (); if (__glibc_unlikely (c == EOF)) input_error (); - else if (c != (unsigned char) *f++) + else if (c != *f++) { ungetc_not_eof (c, s); conv_error (); @@ -484,9 +485,9 @@ __vfscanf_internal (FILE *s, const char *format, va_list argptr, char_buffer_rewind (&charbuf); /* Check for a positional parameter specification. */ - if (ISDIGIT ((UCHAR_T) *f)) + if (ISDIGIT (*f)) { - argpos = read_int ((const UCHAR_T **) &f); + argpos = read_int (&f); if (*f == L_('$')) ++f; else @@ -521,8 +522,8 @@ __vfscanf_internal (FILE *s, const char *format, va_list argptr, /* Find the maximum field width. */ width = 0; - if (ISDIGIT ((UCHAR_T) *f)) - width = read_int ((const UCHAR_T **) &f); + if (ISDIGIT (*f)) + width = read_int (&f); got_width: if (width == 0) width = -1; @@ -2522,12 +2523,11 @@ __vfscanf_internal (FILE *s, const char *format, va_list argptr, } while ((fc = *f++) != '\0' && fc != ']') - if (fc == '-' && *f != '\0' && *f != ']' - && (unsigned char) f[-2] <= (unsigned char) *f) + if (fc == '-' && *f != '\0' && *f != ']' && f[-2] <= *f) { /* Add all characters from the one before the '-' up to (but not including) the next format char. */ - for (fc = (unsigned char) f[-2]; fc < (unsigned char) *f; ++fc) + for (fc = f[-2]; fc < *f; ++fc) ((char *)charbuf.scratch.data)[fc] = 1; } else
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