| Message ID | 20210315155835.1970210-2-richard.henderson@linaro.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Fix qemu_strtosz regression | expand |
On 3/15/21 4:58 PM, Richard Henderson wrote: > Once we've parsed the fractional value, extract it into an integral > 64-bit fraction. Perform the scaling with integer arithemetic, and Typo "arithmetic" > simplify the overflow detection. > > Signed-off-by: Richard Henderson <richard.henderson@linaro.org> > --- > tests/unit/test-cutils.c | 2 +- > util/cutils.c | 50 ++++++++++++++++++++++++++++------------ > 2 files changed, 36 insertions(+), 16 deletions(-) > > diff --git a/tests/unit/test-cutils.c b/tests/unit/test-cutils.c > index bad3a60993..e025b54c05 100644 > --- a/tests/unit/test-cutils.c > +++ b/tests/unit/test-cutils.c > @@ -2128,7 +2128,7 @@ static void test_qemu_strtosz_float(void) > str = "12.345M"; > err = qemu_strtosz(str, &endptr, &res); > g_assert_cmpint(err, ==, 0); > - g_assert_cmpint(res, ==, (uint64_t) (12.345 * MiB)); > + g_assert_cmpint(res, ==, (uint64_t) (12.345 * MiB + 0.5)); > g_assert(endptr == str + 7); > } > > diff --git a/util/cutils.c b/util/cutils.c > index d89a40a8c3..c442882b88 100644 > --- a/util/cutils.c > +++ b/util/cutils.c > @@ -275,10 +275,9 @@ static int do_strtosz(const char *nptr, const char **end, > int retval; > const char *endptr, *f; > unsigned char c; > - bool mul_required = false, hex = false; > - uint64_t val; > + bool hex = false; > + uint64_t val, valf = 0; > int64_t mul; > - double fraction = 0.0; > > /* Parse integral portion as decimal. */ > retval = qemu_strtou64(nptr, &endptr, 10, &val); > @@ -308,17 +307,19 @@ static int do_strtosz(const char *nptr, const char **end, > * without fractional digits. If we see an exponent, treat > * the entire input as invalid instead. > */ > + double fraction; > + > f = endptr; > retval = qemu_strtod_finite(f, &endptr, &fraction); > if (retval) { > - fraction = 0.0; > endptr++; > } else if (memchr(f, 'e', endptr - f) || memchr(f, 'E', endptr - f)) { > endptr = nptr; > retval = -EINVAL; > goto out; > - } else if (fraction != 0) { > - mul_required = true; I'm glad you removed this float-equal warning: util/cutils.c: In function ‘do_strtosz’: util/cutils.c:320:29: error: comparing floating-point with ‘==’ or ‘!=’ is unsafe [-Werror=float-equal] 320 | } else if (fraction != 0) { | ^~ cc1: all warnings being treated as errors > + } else { > + /* Extract into a 64-bit fixed-point fraction. */ > + valf = (uint64_t)(fraction * 0x1p64); > } > } > c = *endptr; > @@ -333,16 +334,35 @@ static int do_strtosz(const char *nptr, const char **end, > mul = suffix_mul(default_suffix, unit); > assert(mul > 0); > } > - if (mul == 1 && mul_required) { > - endptr = nptr; > - retval = -EINVAL; > - goto out; > + if (mul == 1) { > + /* When a fraction is present, a scale is required. */ > + if (valf != 0) { > + endptr = nptr; > + retval = -EINVAL; > + goto out; > + } > + } else { > + uint64_t valh, tmp; > + > + /* Compute exact result: 64.64 x 64.0 -> 128.64 fixed point */ > + mulu64(&val, &valh, val, mul); > + mulu64(&valf, &tmp, valf, mul); > + val += tmp; > + valh += val < tmp; > + > + /* Round 0.5 upward. */ > + tmp = valf >> 63; > + val += tmp; > + valh += val < tmp; > + > + /* Report overflow. */ > + if (valh != 0) { > + retval = -ERANGE; > + goto out; > + } > } > - if (val > (UINT64_MAX - ((uint64_t) (fraction * mul))) / mul) { > - retval = -ERANGE; > - goto out; > - } > - *result = val * mul + (uint64_t) (fraction * mul); > + > + *result = val; > retval = 0; > > out: >
On 3/15/21 10:58 AM, Richard Henderson wrote: > Once we've parsed the fractional value, extract it into an integral > 64-bit fraction. Perform the scaling with integer arithemetic, and > simplify the overflow detection. > > Signed-off-by: Richard Henderson <richard.henderson@linaro.org> > --- > tests/unit/test-cutils.c | 2 +- > util/cutils.c | 50 ++++++++++++++++++++++++++++------------ > 2 files changed, 36 insertions(+), 16 deletions(-) > > diff --git a/tests/unit/test-cutils.c b/tests/unit/test-cutils.c > index bad3a60993..e025b54c05 100644 > --- a/tests/unit/test-cutils.c > +++ b/tests/unit/test-cutils.c > @@ -2128,7 +2128,7 @@ static void test_qemu_strtosz_float(void) > str = "12.345M"; > err = qemu_strtosz(str, &endptr, &res); > g_assert_cmpint(err, ==, 0); > - g_assert_cmpint(res, ==, (uint64_t) (12.345 * MiB)); > + g_assert_cmpint(res, ==, (uint64_t) (12.345 * MiB + 0.5)); This tweak makes sense ;) > g_assert(endptr == str + 7); > } > > diff --git a/util/cutils.c b/util/cutils.c > index d89a40a8c3..c442882b88 100644 > --- a/util/cutils.c > +++ b/util/cutils.c > @@ -275,10 +275,9 @@ static int do_strtosz(const char *nptr, const char **end, > int retval; > const char *endptr, *f; > unsigned char c; > - bool mul_required = false, hex = false; > - uint64_t val; > + bool hex = false; > + uint64_t val, valf = 0; > int64_t mul; > - double fraction = 0.0; > > /* Parse integral portion as decimal. */ > retval = qemu_strtou64(nptr, &endptr, 10, &val); > @@ -308,17 +307,19 @@ static int do_strtosz(const char *nptr, const char **end, > * without fractional digits. If we see an exponent, treat > * the entire input as invalid instead. > */ > + double fraction; > + > f = endptr; > retval = qemu_strtod_finite(f, &endptr, &fraction); > if (retval) { > - fraction = 0.0; dropped, because valf is already 0. Okay. > endptr++; > } else if (memchr(f, 'e', endptr - f) || memchr(f, 'E', endptr - f)) { > endptr = nptr; > retval = -EINVAL; > goto out; > - } else if (fraction != 0) { > - mul_required = true; > + } else { > + /* Extract into a 64-bit fixed-point fraction. */ > + valf = (uint64_t)(fraction * 0x1p64); Nice. > } > } > c = *endptr; > @@ -333,16 +334,35 @@ static int do_strtosz(const char *nptr, const char **end, > mul = suffix_mul(default_suffix, unit); > assert(mul > 0); > } > - if (mul == 1 && mul_required) { > - endptr = nptr; > - retval = -EINVAL; > - goto out; > + if (mul == 1) { > + /* When a fraction is present, a scale is required. */ > + if (valf != 0) { > + endptr = nptr; > + retval = -EINVAL; > + goto out; > + } > + } else { > + uint64_t valh, tmp; > + > + /* Compute exact result: 64.64 x 64.0 -> 128.64 fixed point */ > + mulu64(&val, &valh, val, mul); > + mulu64(&valf, &tmp, valf, mul); > + val += tmp; > + valh += val < tmp; > + > + /* Round 0.5 upward. */ > + tmp = valf >> 63; > + val += tmp; > + valh += val < tmp; > + > + /* Report overflow. */ > + if (valh != 0) { > + retval = -ERANGE; > + goto out; > + } More verbose, but definitely exact. > } > - if (val > (UINT64_MAX - ((uint64_t) (fraction * mul))) / mul) { > - retval = -ERANGE; > - goto out; > - } > - *result = val * mul + (uint64_t) (fraction * mul); > + > + *result = val; > retval = 0; > > out: > Reviewed-by: Eric Blake <eblake@redhat.com>
On 15/03/2021 16.58, Richard Henderson wrote: > Once we've parsed the fractional value, extract it into an integral > 64-bit fraction. Perform the scaling with integer arithemetic, and > simplify the overflow detection. I've put this patch in my local branch, but I'm still getting a failure in the cutils test, this time in the Cirrus-CI with the MinGW build: https://cirrus-ci.com/task/5413753530351616?command=test#L543 Is it related or is this a different bug? Thomas
On 3/17/21 2:09 AM, Thomas Huth wrote: > On 15/03/2021 16.58, Richard Henderson wrote: >> Once we've parsed the fractional value, extract it into an integral >> 64-bit fraction. Perform the scaling with integer arithemetic, and >> simplify the overflow detection. > > I've put this patch in my local branch, but I'm still getting a failure > in the cutils test, this time in the Cirrus-CI with the MinGW build: > > https://cirrus-ci.com/task/5413753530351616?command=test#L543 > > Is it related or is this a different bug? ERROR test-cutils - Bail out! ERROR:../tests/unit/test-cutils.c:2233:test_qemu_strtosz_trailing: assertion failed (res == 0): (1024 == 0) That's testing behavior on: str = "0x"; err = qemu_strtosz(str, &endptr, &res); which should parse as "0" with a suffix of 'x'. It is an independent issue (unrelated to the rounding issues fixed in rth's patch), and rather appears to be a bug in mingw's libc for strtoull although I have not actually set up an environment to test that assumption yet.
On 3/17/21 6:16 AM, Eric Blake wrote: > On 3/17/21 2:09 AM, Thomas Huth wrote: >> On 15/03/2021 16.58, Richard Henderson wrote: >>> Once we've parsed the fractional value, extract it into an integral >>> 64-bit fraction. Perform the scaling with integer arithemetic, and >>> simplify the overflow detection. >> >> I've put this patch in my local branch, but I'm still getting a failure >> in the cutils test, this time in the Cirrus-CI with the MinGW build: >> >> https://cirrus-ci.com/task/5413753530351616?command=test#L543 >> >> Is it related or is this a different bug? > > ERROR test-cutils - Bail out! > ERROR:../tests/unit/test-cutils.c:2233:test_qemu_strtosz_trailing: > assertion failed (res == 0): (1024 == 0) > > That's testing behavior on: > > str = "0x"; > err = qemu_strtosz(str, &endptr, &res); > > which should parse as "0" with a suffix of 'x'. It is an independent > issue (unrelated to the rounding issues fixed in rth's patch), and > rather appears to be a bug in mingw's libc for strtoull although I have > not actually set up an environment to test that assumption yet. Confirmed: $ cat foo.c #include <stdio.h> #include <stdlib.h> #include <errno.h> int main(void) { unsigned long u; const char *str = "0x"; char *end; errno = 0; u = strtoul(str, &end, 10); printf("%lu %s %d\n", u, end, errno); errno = 0; u = strtoul(str, &end, 16); printf("%lu %s %d\n", u, end, errno); str = "0xq"; errno = 0; u = strtoul(str, &end, 10); printf("%lu %s %d\n", u, end, errno); errno = 0; u = strtoul(str, &end, 16); printf("%lu %s %d\n", u, end, errno); return 0; } $ gcc -o foo-linux -Wall foo.c $ x86_64-w64-mingw32-gcc -o foo-mingw -Wall foo.c $ ./foo-linux 0 x 0 0 x 0 0 xq 0 0 xq 0 $ wine ./foo-mingw 2>/dev/null 0 x 0 0 0x 0 0 xq 0 0 0xq 0 Mingw has a bug (and therefore so do all our qemu_strto* functions) when parsing "0xgarbage" with a base of 0 or 16, in that it fails to advance past the leading '0' (which is a valid parse). Patch coming up.
diff --git a/tests/unit/test-cutils.c b/tests/unit/test-cutils.c index bad3a60993..e025b54c05 100644 --- a/tests/unit/test-cutils.c +++ b/tests/unit/test-cutils.c @@ -2128,7 +2128,7 @@ static void test_qemu_strtosz_float(void) str = "12.345M"; err = qemu_strtosz(str, &endptr, &res); g_assert_cmpint(err, ==, 0); - g_assert_cmpint(res, ==, (uint64_t) (12.345 * MiB)); + g_assert_cmpint(res, ==, (uint64_t) (12.345 * MiB + 0.5)); g_assert(endptr == str + 7); } diff --git a/util/cutils.c b/util/cutils.c index d89a40a8c3..c442882b88 100644 --- a/util/cutils.c +++ b/util/cutils.c @@ -275,10 +275,9 @@ static int do_strtosz(const char *nptr, const char **end, int retval; const char *endptr, *f; unsigned char c; - bool mul_required = false, hex = false; - uint64_t val; + bool hex = false; + uint64_t val, valf = 0; int64_t mul; - double fraction = 0.0; /* Parse integral portion as decimal. */ retval = qemu_strtou64(nptr, &endptr, 10, &val); @@ -308,17 +307,19 @@ static int do_strtosz(const char *nptr, const char **end, * without fractional digits. If we see an exponent, treat * the entire input as invalid instead. */ + double fraction; + f = endptr; retval = qemu_strtod_finite(f, &endptr, &fraction); if (retval) { - fraction = 0.0; endptr++; } else if (memchr(f, 'e', endptr - f) || memchr(f, 'E', endptr - f)) { endptr = nptr; retval = -EINVAL; goto out; - } else if (fraction != 0) { - mul_required = true; + } else { + /* Extract into a 64-bit fixed-point fraction. */ + valf = (uint64_t)(fraction * 0x1p64); } } c = *endptr; @@ -333,16 +334,35 @@ static int do_strtosz(const char *nptr, const char **end, mul = suffix_mul(default_suffix, unit); assert(mul > 0); } - if (mul == 1 && mul_required) { - endptr = nptr; - retval = -EINVAL; - goto out; + if (mul == 1) { + /* When a fraction is present, a scale is required. */ + if (valf != 0) { + endptr = nptr; + retval = -EINVAL; + goto out; + } + } else { + uint64_t valh, tmp; + + /* Compute exact result: 64.64 x 64.0 -> 128.64 fixed point */ + mulu64(&val, &valh, val, mul); + mulu64(&valf, &tmp, valf, mul); + val += tmp; + valh += val < tmp; + + /* Round 0.5 upward. */ + tmp = valf >> 63; + val += tmp; + valh += val < tmp; + + /* Report overflow. */ + if (valh != 0) { + retval = -ERANGE; + goto out; + } } - if (val > (UINT64_MAX - ((uint64_t) (fraction * mul))) / mul) { - retval = -ERANGE; - goto out; - } - *result = val * mul + (uint64_t) (fraction * mul); + + *result = val; retval = 0; out:
Once we've parsed the fractional value, extract it into an integral 64-bit fraction. Perform the scaling with integer arithemetic, and simplify the overflow detection. Signed-off-by: Richard Henderson <richard.henderson@linaro.org> --- tests/unit/test-cutils.c | 2 +- util/cutils.c | 50 ++++++++++++++++++++++++++++------------ 2 files changed, 36 insertions(+), 16 deletions(-)