[Bug 2052929] Re: failed autopkgtests for evolver vs glibc 2.39 on amd64

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------------------------------------------------------------------------
On 2024-03-30T12:48:10+00:00 Doko-v wrote:

reported at
https://gcc.gnu.org/pipermail/gcc-patches/2024-March/647635.html

On x86, this compiles into movdqa which segfaults on unaligned access.

This kind of failure has been seen when running against glibc 2.39,
which incidentally changed the printf implementation to move away from
alloca() for this data to instead append it at the end of an existing
"scratch buffer", with arbitrary alignment, whereas alloca() was
probably more likely to be naturally aligned.

Tested by adding the patch to the Ubuntu gcc-14 package in
https://launchpad.net/~schopin/+archive/ubuntu/libquadmath

Signed-off-by: Simon Chopin <simon.chopin at canonical.com>
---
 libquadmath/printf/printf_fp.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/libquadmath/printf/printf_fp.c b/libquadmath/printf/printf_fp.c
index 8effcee88fa..d86aa650d38 100644
--- a/libquadmath/printf/printf_fp.c
+++ b/libquadmath/printf/printf_fp.c
@@ -363,7 +363,7 @@ __quadmath_printf_fp (struct __quadmath_printf_file *fp,
 
   /* Fetch the argument value.	*/
     {
-      fpnum = **(const __float128 **) args[0];
+      memcpy(&fpnum, *(void* const *) args[0], sizeof(fpnum));
 
       /* Check for special values: not a number or infinity.  */
       if (isnanq (fpnum))

Reply at:
https://bugs.launchpad.net/ubuntu/+source/glibc/+bug/2052929/comments/4


** Changed in: gcc
       Status: Unknown => New

** Changed in: gcc
   Importance: Unknown => Medium

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https://bugs.launchpad.net/bugs/2052929

Title:
  failed autopkgtests for evolver vs glibc 2.39 on amd64

Status in gcc:
  New
Status in evolver package in Ubuntu:
  New
Status in gcc-13 package in Ubuntu:
  New
Status in gcc-14 package in Ubuntu:
  In Progress
Status in glibc package in Ubuntu:
  Invalid
Status in evolver package in Debian:
  New

Bug description:
  The autopkgests for evolver fail when run against glibc 2.39 on amd64
  with a segfault:

  3537s autopkgtest [09:43:29]: test command6: [-----------------------
  3537s Surface Evolver Version 2.70a (Debian 2.70+ds-8build1), August 27, 2013, 64-bit.
  3537s Compiled for float128, 33 digits precision.
  3537s Built with Geomview support.
  3537s 
  3537s Enter command: 
  3537s Enter command: // Typical evolution to sphere
  3537s Enter command: gogo := { g 5; r; g 5; hessian; r; g 5; hessian; }
  3537s Enter command: 
  3537s Enter command: // Evolution to very high accuracy, using higher-order Lagrange elements.
  3537s Enter command: // To be run on original datafile.
  3537s Enter command: gogo2 := { g 5; r; g 5; hessian; r; g 5; hessian;
  3537s more>            lagrange 2; g 5; hessian; 
  3537s more>            lagrange 4; g 5; hessian; 
  3537s more>            lagrange 6; g 5; hessian; 
  3537s more>            ideal_rad := (3*body[1].volume/4/pi)^(1/3);
  3537s more>            printf "Area error: %g\n",total_area - 4*pi*ideal_rad^2;
  3537s more>            printf "Vertex radius spread: %g\n",
  3537s more>              max(vertex,sqrt((x-.5)^2+(y-.5)^2+(z-.5)^2))
  3537s more>                - min(vertex,sqrt((x-.5)^2+(y-.5)^2+(z-.5)^2));
  3537s more> }
  3537s Enter command: g 5; v; r ; g 10; v;
  3537s bash: line 1:  1012 Done                    echo "g 5; v; r ; g 10; v;"
  3537s       1013 Segmentation fault      (core dumped) | evolver-nox-q cube

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