https://gcc.gnu.org/bugzilla/show_bug.cgi?id=128594
Bug ID: 128594
Summary: flag_instrument_functions_exclude_p queries
decl_printable_name at verbosity 1, making
-finstrument-functions-exclude-function-list unable to
match C++ parameter or return types as documented in
invoke.texi
Product: gcc
Version: 16.2.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: 220245569 at seu dot edu.cn
CC: 220255623 at seu dot edu.cn, jianhao.xu at seu dot edu.cn
Target Milestone: ---
Target: *-*-*
Reproducer
----------
$ cat trigger.cpp
namespace ns {
int blah(int x) { return x + 1; }
}
int main() { return ns::blah(41); }
Compile command / flags:
podman exec defuzz-toolchain-daemon /opt/gcc16/bin/x86_64-linux-gnu-g++ -O0
-finstrument-functions '-finstrument-functions-exclude-function-list=int
ns::blah(int)' -S -o - /tmp/t13.cpp | grep -A12 '_ZN2ns4blahEi:'
Observed output (GCC 16.2.0):
_ZN2ns4blahEi:
.LFB0:
.cfi_startproc
pushq %rbp
.cfi_def_cfa_offset 16
.cfi_offset 6, -16
movq %rsp, %rbp
.cfi_def_cfa_register 6
subq $16, %rsp
movl %edi, -4(%rbp)
movq 8(%rbp), %rax
movq %rax, %rsi
movl $_ZN2ns4blahEi, %edi
call __cyg_profile_func_enter
Expected behavior:
-finstrument-functions-exclude-function-list must either match against
verbosity-2 decl_printable_name (which includes the C++ signature as documented
in invoke.texi:18232-18234) in addition to verbosity-1, or invoke.texi must
match the implementation.
Root cause
----------
Source location: gcc/gimplify.cc:21895-21912
(flag_instrument_functions_exclude_p), gcc/cp/error.cc:3659-3677
(lang_decl_name), gcc/doc/invoke.texi:18232-18234
gcc/doc/invoke.texi:18232-18234 explicitly documents that for
-finstrument-functions-exclude-function-list=sym,sym,..., 'In C++, the function
name includes the function signature, for example: vector<int> blah(const
vector<int> &).' However, flag_instrument_functions_exclude_p
(gcc/gimplify.cc:21900) obtains the function name via 'name =
lang_hooks.decl_printable_name (fndecl, 1);'. In the C++ front end,
cxx_printable_name_internal -> lang_decl_name (gcc/cp/error.cc:3659-3677) only
sets TFF_DECL_SPECIFIERS (return type) and prints the parameter list when
verbosity >= 2; for v == 1, it prints only the scope-qualified name
('ns::blah') without return type or parameter types! Consequently, passing any
C++ signature with parameter types or return type as documented in invoke.texi
(or trying to exclude one C++ overload without excluding all overloads of the
same name) never matches.
Impact:
C++ functions intended to be excluded from
__cyg_profile_func_enter/__cyg_profile_func_exit (such as low-level hooks or
specific overloads specified by signature per invoke.texi) remain instrumented,
causing infinite recursion in profiling/tracing hooks or failing to exclude
targeted C++ overloads.
Suggested Fix
-------------
In gcc/gimplify.cc:21900 (flag_instrument_functions_exclude_p), check both
lang_hooks.decl_printable_name (fndecl, 1) and lang_hooks.decl_printable_name
(fndecl, 2) against vec_char_p (flag_instrument_functions_exclude_functions).
