International audienceWe report on a case study that was conducted as part of an industrial research project on static analysis of critical C code. The example program considered in this paper is an excerpt of an industrial code, only slightly modified for confidentiality reasons, involving floating-point computations. The objective was to establish a property on the functional behavior of this code, taking into account rounding errors made during computations. The property is formalized using ACSL, the behavioral specification language available inside the Frama-C environment, and it is verified by automated theorem proving