Math library models: add missing *BSD variants, cleanup

[tautschnig]

BSD systems appear to use __ prefixed variants of several functions. Define these as needed. Also, avoid handling some GCC-style __builtin_-prefixed functions via models when others are done directly in the type checker: do all of them in the type checker.

In addition to __builtin_isfinite, recognise its older glibc internal aliases __builtin_finite, __builtin_finitef and __builtin_finitel in the same isfinite_exprt branch of the type checker. Some glibc <bits/mathcalls-helper-functions.h> headers expose the legacy finite() API via these builtins, and without recognition CBMC would otherwise treat them as body-less functions returning nondet.

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[Copilot]

Pull request overview

Adds BSD-style __-prefixed math library models (e.g., __isfinite, __isnand, __isnormal, __signbitl, __isfinitef/l), moves several GCC __builtin_* functions (fabs variants, isnan/isinf/finite variants) from library models into the C type checker for consistent direct handling, and replaces internal uses of __builtin_inf* in math.c with __CPROVER_inf*. Updates library_check.sh to filter the newly added/relocated symbols, and replaces the old KNOWNBUG placeholder tests with real assertion-based regression tests.

Changes:

• Add BSD __-prefixed math library function models and remove __builtin_fabs[fl] models now handled in the type checker.
• Extend c_typecheck_expr to recognize __builtin_fabs[fl], __builtin_isnan[fl], __builtin_isinf[fl], __builtin_isfinite, __builtin_finite[fl] directly.
• Replace KNOWNBUG regression stubs with real assertion-based tests for isfinite/isinf/isnormal/signbit/fpclassify and their __/__builtin_ variants; update library_check.sh filters accordingly.

Reviewed changes

Copilot reviewed 42 out of 42 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
src/ansi-c/library/math.c	Remove __builtin_fabs* models, add BSD __isfinite*/__isnand/__isnormal*/__signbitl, replace __builtin_inf* calls with __CPROVER_inf*.
src/ansi-c/c_typecheck_expr.cpp	Extend special-function handling for __builtin_fabs/isnan/isinf/isfinite/finite variants.
src/ansi-c/library_check.sh	Filter additional __-prefixed and is*[fl] symbols added in models.
regression/cbmc-library/isfinite/{main.c,test.desc}	Replace KNOWNBUG stub with real isfinite assertions; promote to CORE.
regression/cbmc-library/isnormal/{main.c,test.desc}	Replace stub with __builtin_isnormal static-assert test; promote to CORE.
regression/cbmc-library/isinf/main.c	Add __builtin_isinf / __builtin_isinf_sign runtime and static assertions.
regression/cbmc-library/signbit/main.c	Add real signbit assertions for double and long double.
regression/cbmc-library/__fpclassify/main.c	Add fpclassify and __builtin_fpclassify runtime and static assertions.
regression/cbmc-library/{__isinf,__isinff,__isinfl,__isnan,__isnanf,__isnanl,__isnormalf,__signbit,__signbitf,__builtin_fabs,__builtin_fabsf,__builtin_fabsl,isinff,isinfl,isnanf,isnanl}/*	Delete obsolete KNOWNBUG placeholder tests now covered by typechecker handling and library_check filters.

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 80.59%. Comparing base (cbdcf13) to head (b165f10).

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #9020      +/-   ##
===========================================
- Coverage    80.60%   80.59%   -0.01%     
===========================================
  Files         1711     1711              
  Lines       189454   189460       +6     
  Branches        73       73              
===========================================
- Hits        152712   152699      -13     
- Misses       36742    36761      +19     

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