Duncan Murdoch
2021-Sep-10 16:12 UTC
[Rd] Spurious warnings in coercion from double/complex/character to raw
On 10/09/2021 11:29 a.m., Herv? Pag?s wrote:> Hi, > > The first warning below is unexpected and confusing: > > > as.raw(c(3e9, 5.1)) > [1] 00 05 > Warning messages: > 1: NAs introduced by coercion to integer range > 2: out-of-range values treated as 0 in coercion to raw > > The reason we get it is that coercion from numeric to raw is currently > implemented on top of coercion from numeric to int (file > src/main/coerce.c, lines 700-710): > > case REALSXP: > for (i = 0; i < n; i++) { > // if ((i+1) % NINTERRUPT == 0) R_CheckUserInterrupt(); > tmp = IntegerFromReal(REAL_ELT(v, i), &warn); > if(tmp == NA_INTEGER || tmp < 0 || tmp > 255) { > tmp = 0; > warn |= WARN_RAW; > } > pa[i] = (Rbyte) tmp; > } > break; > > The first warning comes from the call to IntegerFromReal(). > > The following code avoids the spurious warning and is also simpler and > slightly faster: > > case REALSXP: > for (i = 0; i < n; i++) { > // if ((i+1) % NINTERRUPT == 0) R_CheckUserInterrupt(); > double vi = REAL_ELT(v, i); > if(ISNAN(vi) || (tmp = (int) vi) < 0 || tmp > 255) { > tmp = 0; > warn |= WARN_RAW; > } > pa[i] = (Rbyte) tmp; > } > break;Doesn't that give different results in case vi is so large that "(int) vi" overflows? (I don't know what the C standard says, but some online references say that behaviour is implementation dependent.) For example, if vi = 1.0 + INT_MAX; wouldn't "(int) vi" be equal to a small integer? Duncan Murdoch> > Coercion from complex to raw has the same problem: > > > as.raw(c(3e9+0i, 5.1)) > [1] 00 05 > Warning messages: > 1: NAs introduced by coercion to integer range > 2: out-of-range values treated as 0 in coercion to raw > > Current implementation (file src/main/coerce.c, lines 711-721): > > case CPLXSXP: > for (i = 0; i < n; i++) { > // if ((i+1) % NINTERRUPT == 0) R_CheckUserInterrupt(); > tmp = IntegerFromComplex(COMPLEX_ELT(v, i), &warn); > if(tmp == NA_INTEGER || tmp < 0 || tmp > 255) { > tmp = 0; > warn |= WARN_RAW; > } > pa[i] = (Rbyte) tmp; > } > break; > > This implementation has the following additional problem when the > supplied complex has a nonzero imaginary part: > > > as.raw(300+4i) > [1] 00 > Warning messages: > 1: imaginary parts discarded in coercion > 2: out-of-range values treated as 0 in coercion to raw > > > as.raw(3e9+4i) > [1] 00 > Warning messages: > 1: NAs introduced by coercion to integer range > 2: out-of-range values treated as 0 in coercion to raw > > In one case we get a warning about the discarding of the imaginary part > but not the other case, which is unexpected. We should see the exact > same warning (or warnings) in both cases. > > With the following fix we only get the warning about the discarding of > the imaginary part if we are not in a "out-of-range values treated as 0 > in coercion to raw" situation: > > case CPLXSXP: > for (i = 0; i < n; i++) { > // if ((i+1) % NINTERRUPT == 0) R_CheckUserInterrupt(); > Rcomplex vi = COMPLEX_ELT(v, i); > if(ISNAN(vi.r) || ISNAN(vi.i) || (tmp = (int) vi.r) < 0 || > tmp > 255) { > tmp = 0; > warn |= WARN_RAW; > } else { > if(vi.i != 0.0) > warn |= WARN_IMAG; > } > pa[i] = (Rbyte) tmp; > } > break; > > Finally, coercion from character to raw has the same problem and its > code can be fixed in a similar manner: > > > as.raw(c("3e9", 5.1)) > [1] 00 05 > Warning messages: > 1: NAs introduced by coercion to integer range > 2: out-of-range values treated as 0 in coercion to raw > > Cheers, > H. > >
GILLIBERT, Andre
2021-Sep-10 16:36 UTC
[Rd] Spurious warnings in coercion from double/complex/character to raw
Hello, Integer overflow is undefined behavior by the C standard. For instance, on my computer, with GCC 5.4.0, with the optimization level 2, the following program never stops: include <stdio.h> int main(void) { for(int i=1; i != 0; i++) { if ((i & 0xFFFFFFF) == 0) { printf("%d\n", i); } } } This is due to a compiler optimization, that assumes that the integer can never overflow, and so, can never be equal to zero, and so, the for loop should never stops. You should always be very cautious when adding two integers, to avoid any overflow. There is no problem with unsigned integers. Similarly, double-to-integer conversions are only safe if the double is in the range [INT_MIN to INT_MAX] The standard contains: When a finite value of real floating type is converted to an integer type other than _Bool, the fractional part is discarded (i.e., the value is truncated toward zero). If the value of the integral part cannot be represented by the integer type, the behavior is undefined The easiest solution to avoid a risk when converting, is to check that the double (e.g. vi) is in range [0 to 255] BEFORE converting to an integer. -- Sincerely Andr? GILLIBERT ________________________________ De : R-devel <r-devel-bounces at r-project.org> de la part de Duncan Murdoch <murdoch.duncan at gmail.com> Envoy? : vendredi 10 septembre 2021 18:12:02 ? : Herv? Pag?s; r-devel Objet : Re: [Rd] Spurious warnings in coercion from double/complex/character to raw ATTENTION: Cet e-mail provient d?une adresse mail ext?rieure au CHU de Rouen. Ne cliquez pas sur les liens ou n'ouvrez pas les pi?ces jointes ? moins de conna?tre l'exp?diteur et de savoir que le contenu est s?r. En cas de doute, transf?rer le mail ? ? DSI, S?curit? ? pour analyse. Merci de votre vigilance On 10/09/2021 11:29 a.m., Herv? Pag?s wrote:> Hi, > > The first warning below is unexpected and confusing: > > > as.raw(c(3e9, 5.1)) > [1] 00 05 > Warning messages: > 1: NAs introduced by coercion to integer range > 2: out-of-range values treated as 0 in coercion to raw > > The reason we get it is that coercion from numeric to raw is currently > implemented on top of coercion from numeric to int (file > src/main/coerce.c, lines 700-710): > > case REALSXP: > for (i = 0; i < n; i++) { > // if ((i+1) % NINTERRUPT == 0) R_CheckUserInterrupt(); > tmp = IntegerFromReal(REAL_ELT(v, i), &warn); > if(tmp == NA_INTEGER || tmp < 0 || tmp > 255) { > tmp = 0; > warn |= WARN_RAW; > } > pa[i] = (Rbyte) tmp; > } > break; > > The first warning comes from the call to IntegerFromReal(). > > The following code avoids the spurious warning and is also simpler and > slightly faster: > > case REALSXP: > for (i = 0; i < n; i++) { > // if ((i+1) % NINTERRUPT == 0) R_CheckUserInterrupt(); > double vi = REAL_ELT(v, i); > if(ISNAN(vi) || (tmp = (int) vi) < 0 || tmp > 255) { > tmp = 0; > warn |= WARN_RAW; > } > pa[i] = (Rbyte) tmp; > } > break;Doesn't that give different results in case vi is so large that "(int) vi" overflows? (I don't know what the C standard says, but some online references say that behaviour is implementation dependent.) For example, if vi = 1.0 + INT_MAX; wouldn't "(int) vi" be equal to a small integer? Duncan Murdoch> > Coercion from complex to raw has the same problem: > > > as.raw(c(3e9+0i, 5.1)) > [1] 00 05 > Warning messages: > 1: NAs introduced by coercion to integer range > 2: out-of-range values treated as 0 in coercion to raw > > Current implementation (file src/main/coerce.c, lines 711-721): > > case CPLXSXP: > for (i = 0; i < n; i++) { > // if ((i+1) % NINTERRUPT == 0) R_CheckUserInterrupt(); > tmp = IntegerFromComplex(COMPLEX_ELT(v, i), &warn); > if(tmp == NA_INTEGER || tmp < 0 || tmp > 255) { > tmp = 0; > warn |= WARN_RAW; > } > pa[i] = (Rbyte) tmp; > } > break; > > This implementation has the following additional problem when the > supplied complex has a nonzero imaginary part: > > > as.raw(300+4i) > [1] 00 > Warning messages: > 1: imaginary parts discarded in coercion > 2: out-of-range values treated as 0 in coercion to raw > > > as.raw(3e9+4i) > [1] 00 > Warning messages: > 1: NAs introduced by coercion to integer range > 2: out-of-range values treated as 0 in coercion to raw > > In one case we get a warning about the discarding of the imaginary part > but not the other case, which is unexpected. We should see the exact > same warning (or warnings) in both cases. > > With the following fix we only get the warning about the discarding of > the imaginary part if we are not in a "out-of-range values treated as 0 > in coercion to raw" situation: > > case CPLXSXP: > for (i = 0; i < n; i++) { > // if ((i+1) % NINTERRUPT == 0) R_CheckUserInterrupt(); > Rcomplex vi = COMPLEX_ELT(v, i); > if(ISNAN(vi.r) || ISNAN(vi.i) || (tmp = (int) vi.r) < 0 || > tmp > 255) { > tmp = 0; > warn |= WARN_RAW; > } else { > if(vi.i != 0.0) > warn |= WARN_IMAG; > } > pa[i] = (Rbyte) tmp; > } > break; > > Finally, coercion from character to raw has the same problem and its > code can be fixed in a similar manner: > > > as.raw(c("3e9", 5.1)) > [1] 00 05 > Warning messages: > 1: NAs introduced by coercion to integer range > 2: out-of-range values treated as 0 in coercion to raw > > Cheers, > H. > >______________________________________________ R-devel at r-project.org mailing list stat.ethz.ch/mailman/listinfo/r-devel [[alternative HTML version deleted]]
Hervé Pagès
2021-Sep-10 19:13 UTC
[Rd] Spurious warnings in coercion from double/complex/character to raw
On 10/09/2021 09:12, Duncan Murdoch wrote:> On 10/09/2021 11:29 a.m., Herv? Pag?s wrote: >> Hi, >> >> The first warning below is unexpected and confusing: >> >> ??? > as.raw(c(3e9, 5.1)) >> ??? [1] 00 05 >> ??? Warning messages: >> ??? 1: NAs introduced by coercion to integer range >> ??? 2: out-of-range values treated as 0 in coercion to raw >> >> The reason we get it is that coercion from numeric to raw is currently >> implemented on top of coercion from numeric to int (file >> src/main/coerce.c, lines 700-710): >> >> ????? case REALSXP: >> ????????? for (i = 0; i < n; i++) { >> //????????? if ((i+1) % NINTERRUPT == 0) R_CheckUserInterrupt(); >> ????????????? tmp = IntegerFromReal(REAL_ELT(v, i), &warn); >> ????????????? if(tmp == NA_INTEGER || tmp < 0 || tmp > 255) { >> ????????????????? tmp = 0; >> ????????????????? warn |= WARN_RAW; >> ????????????? } >> ????????????? pa[i] = (Rbyte) tmp; >> ????????? } >> ????????? break; >> >> The first warning comes from the call to IntegerFromReal(). >> >> The following code avoids the spurious warning and is also simpler and >> slightly faster: >> >> ????? case REALSXP: >> ????????? for (i = 0; i < n; i++) { >> //????????? if ((i+1) % NINTERRUPT == 0) R_CheckUserInterrupt(); >> ????????????? double vi = REAL_ELT(v, i); >> ????????????? if(ISNAN(vi) || (tmp = (int) vi) < 0 || tmp > 255) { >> ????????????????? tmp = 0; >> ????????????????? warn |= WARN_RAW; >> ????????????? } >> ????????????? pa[i] = (Rbyte) tmp; >> ????????? } >> ????????? break; > > Doesn't that give different results in case vi is so large that "(int) > vi" overflows?? (I don't know what the C standard says, but some online > references say that behaviour is implementation dependent.) > > For example, if > > ? vi = 1.0 +? INT_MAX; > > wouldn't "(int) vi" be equal to a small integer?Good catch, thanks! Replacing if(ISNAN(vi) || (tmp = (int) vi) < 0 || tmp > 255) { tmp = 0; warn |= WARN_RAW; } pa[i] = (Rbyte) tmp; with if(ISNAN(vi) || vi <= -1.0 || vi >= 256.0) { tmp = 0; warn |= WARN_RAW; } else { tmp = (int) vi; } pa[i] = (Rbyte) tmp; should address that. FWIW IntegerFromReal() has a similar risk of int overflow (src/main/coerce.c, lines 128-138): int attribute_hidden IntegerFromReal(double x, int *warn) { if (ISNAN(x)) return NA_INTEGER; else if (x >= INT_MAX+1. || x <= INT_MIN ) { *warn |= WARN_INT_NA; return NA_INTEGER; } return (int) x; } The cast to int will also be an int overflow situation if x is > INT_MAX and < INT_MAX+1 so the risk is small! There are other instances of this situation in IntegerFromComplex() and IntegerFromString(). More below...> > Duncan Murdoch > > >> >> Coercion from complex to raw has the same problem: >> >> ??? > as.raw(c(3e9+0i, 5.1)) >> ??? [1] 00 05 >> ??? Warning messages: >> ??? 1: NAs introduced by coercion to integer range >> ??? 2: out-of-range values treated as 0 in coercion to raw >> >> Current implementation (file src/main/coerce.c, lines 711-721): >> >> ????? case CPLXSXP: >> ????????? for (i = 0; i < n; i++) { >> //????????? if ((i+1) % NINTERRUPT == 0) R_CheckUserInterrupt(); >> ????????????? tmp = IntegerFromComplex(COMPLEX_ELT(v, i), &warn); >> ????????????? if(tmp == NA_INTEGER || tmp < 0 || tmp > 255) { >> ????????????????? tmp = 0; >> ????????????????? warn |= WARN_RAW; >> ????????????? } >> ????????????? pa[i] = (Rbyte) tmp; >> ????????? } >> ????????? break; >> >> This implementation has the following additional problem when the >> supplied complex has a nonzero imaginary part: >> >> ??? > as.raw(300+4i) >> ??? [1] 00 >> ??? Warning messages: >> ??? 1: imaginary parts discarded in coercion >> ??? 2: out-of-range values treated as 0 in coercion to raw >> >> ??? > as.raw(3e9+4i) >> ??? [1] 00 >> ??? Warning messages: >> ??? 1: NAs introduced by coercion to integer range >> ??? 2: out-of-range values treated as 0 in coercion to raw >> >> In one case we get a warning about the discarding of the imaginary part >> but not the other case, which is unexpected. We should see the exact >> same warning (or warnings) in both cases. >> >> With the following fix we only get the warning about the discarding of >> the imaginary part if we are not in a "out-of-range values treated as 0 >> in coercion to raw" situation: >> >> ????? case CPLXSXP: >> ????????? for (i = 0; i < n; i++) { >> //????????? if ((i+1) % NINTERRUPT == 0) R_CheckUserInterrupt(); >> ????????????? Rcomplex vi = COMPLEX_ELT(v, i); >> ????????????? if(ISNAN(vi.r) || ISNAN(vi.i) || (tmp = (int) vi.r) < 0 || >> tmp > 255) { >> ????????????????? tmp = 0; >> ????????????????? warn |= WARN_RAW; >> ????????????? } else { >> ????????????????? if(vi.i != 0.0) >> ????????????????????? warn |= WARN_IMAG; >> ????????????? } >> ????????????? pa[i] = (Rbyte) tmp; >> ????????? } >> ????????? break;Corrected version: if(ISNAN(vi.r) || ISNAN(vi.i) || vi.r <= -1.00 || vi.r >= 256.00) { tmp = 0; warn |= WARN_RAW; } else { tmp = (int) vi.r; if(vi.i != 0.0) warn |= WARN_IMAG; } pa[i] = (Rbyte) tmp; Hopefully this time I got it right. Best, H.>> >> Finally, coercion from character to raw has the same problem and its >> code can be fixed in a similar manner: >> >> ??? > as.raw(c("3e9", 5.1)) >> ??? [1] 00 05 >> ??? Warning messages: >> ??? 1: NAs introduced by coercion to integer range >> ??? 2: out-of-range values treated as 0 in coercion to raw >> >> Cheers, >> H. >> >> >-- Herv? Pag?s Bioconductor Core Team hpages.on.github at gmail.com