From 34947d4e97ee72b26491cfe5ff4fa8258fadbe95 Mon Sep 17 00:00:00 2001 From: Patrick Palka Date: Fri, 24 Sep 2021 12:36:26 -0400 Subject: [PATCH] real: fix encoding of negative IEEE double/quad values [PR98216] In encode_ieee_double/quad, the assignment unsigned long WORD = r->sign << 31; is intended to set the 31st bit of WORD whenever the sign bit is set. But on LP64 hosts it also unintentionally sets the upper 32 bits of WORD, because r->sign gets promoted from unsigned:1 to int and then the result of the shift (equal to INT_MIN) gets sign extended from int to long. In the C++ frontend, this bug causes incorrect mangling of negative floating point values because the output of real_to_target called from write_real_cst unexpectedly has the upper 32 bits of this word set, which the caller doesn't mask out. This patch fixes this by avoiding the unwanted sign extension. Note that r0-53976 fixed the same bug in encode_ieee_single long ago. PR c++/98216 PR c++/91292 gcc/ChangeLog: * real.c (encode_ieee_double): Avoid unwanted sign extension. (encode_ieee_quad): Likewise. gcc/testsuite/ChangeLog: * g++.dg/cpp2a/nontype-float2.C: New test. --- gcc/real.c | 6 ++++-- gcc/testsuite/g++.dg/cpp2a/nontype-float2.C | 14 ++++++++++++++ 2 files changed, 18 insertions(+), 2 deletions(-) create mode 100644 gcc/testsuite/g++.dg/cpp2a/nontype-float2.C diff --git a/gcc/real.c b/gcc/real.c index 555cf44..8c7a47a 100644 --- a/gcc/real.c +++ b/gcc/real.c @@ -3150,9 +3150,10 @@ encode_ieee_double (const struct real_format *fmt, long *buf, const REAL_VALUE_TYPE *r) { unsigned long image_lo, image_hi, sig_lo, sig_hi, exp; + unsigned long sign = r->sign; bool denormal = (r->sig[SIGSZ-1] & SIG_MSB) == 0; - image_hi = r->sign << 31; + image_hi = sign << 31; image_lo = 0; if (HOST_BITS_PER_LONG == 64) @@ -3938,10 +3939,11 @@ encode_ieee_quad (const struct real_format *fmt, long *buf, const REAL_VALUE_TYPE *r) { unsigned long image3, image2, image1, image0, exp; + unsigned long sign = r->sign; bool denormal = (r->sig[SIGSZ-1] & SIG_MSB) == 0; REAL_VALUE_TYPE u; - image3 = r->sign << 31; + image3 = sign << 31; image2 = 0; image1 = 0; image0 = 0; diff --git a/gcc/testsuite/g++.dg/cpp2a/nontype-float2.C b/gcc/testsuite/g++.dg/cpp2a/nontype-float2.C new file mode 100644 index 0000000..40b42b9 --- /dev/null +++ b/gcc/testsuite/g++.dg/cpp2a/nontype-float2.C @@ -0,0 +1,14 @@ +// PR c++/98216 +// PR c++/91292 +// { dg-do compile { target c++20 } } + +template void f() { } + +template void f<-1.0f>(); +template void f<-2.0f>(); + +template void f<-1.0>(); +template void f<-2.0>(); + +template void f<-1.0L>(); +template void f<-2.0L>(); -- 2.7.4