https://gcc.gnu.org/bugzilla/show_bug.cgi?id=125535
--- Comment #3 from GCC Commits <cvs-commit at gcc dot gnu.org> --- The releases/gcc-16 branch has been updated by Jerry DeLisle <[email protected]>: https://gcc.gnu.org/g:d1750d8df75f292a0111e94dda82664c988bcc60 commit r16-9101-gd1750d8df75f292a0111e94dda82664c988bcc60 Author: Jerry DeLisle <[email protected]> Date: Fri Jun 5 13:20:05 2026 -0700 fortran: wrong-code for implied-do with allocatable-component derived type When a nested implied-do array constructor called a transformational intrinsic (e.g. RESHAPE) whose result type has allocatable components, the argument temporaries were freed before the result's allocatable components were deep-copied, causing a heap-use-after-free and wrong runtime values. The root cause: in gfc_conv_procedure_call, the call to gfc_add_block_to_block (&se->pre, &post) â which frees the allocatable components of argument temporaries â was issued before the deep-copy loop for the result's allocatable components. Transformational library functions such as RESHAPE do a shallow byte-copy of the source array into the result, so the result's component pointers alias those of the argument temporaries. Freeing the temporaries first and then copying yielded use-after-free. Fix: move gfc_add_block_to_block (&se->pre, &post) to after the deep-copy loop, so that the result's allocatable components are copied while the source storage is still live. PR fortran/125535 Assisted-by: Claude Sonnet 4.6 gcc/fortran/ChangeLog: PR fortran/125535 * trans-expr.cc (gfc_conv_procedure_call): Move post block append to after the deep copy of allocatable components for transformational intrinsics, so that argument temporaries are not freed before the result components are copied. gcc/testsuite/ChangeLog: PR fortran/125535 * gfortran.dg/implied_do_alloc_comp_1.f90: New test. (cherry picked from commit a0d7e1c3639a6e19f4413bf53bb1e994494ec77f)
