https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96383
Bug ID: 96383
Summary: Full ABI information missing missing from GCC compiled
C
Product: gcc
Version: 10.1.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: woodard at redhat dot com
Target Milestone: ---
When GCC compiles C and there is a call to an external function the full ABI
information for the function being called doesn't exist in the caller.
For example compiling bzip2 with gcc 10.1.1 this is all that you get for the
function fflush.
[ 93a4] subprogram abbrev: 96
external (flag_present) yes
declaration (flag_present) yes
linkage_name (strp) "fflush"
name (strp) "fflush"
decl_file (data1) stdio.h (6)
decl_line (data1) 218
decl_column (data1) 12
However when you compile the same library with clang you get much more
information:
[ 49ec] subprogram abbrev: 26
name (strp) "fflush"
decl_file (data1) stdio.h (3)
decl_line (data1) 218
prototyped (flag_present) yes
type (ref4) [ 425e]
declaration (flag_present) yes
external (flag_present) yes
[ 49f7] formal_parameter abbrev: 7
type (ref4) [ 47c7]
[ 47c7] pointer_type abbrev: 3
type (ref4) [ 47cc]
[ 47cc] structure_type abbrev: 21
name (strp) "_IO_FILE"
byte_size (data1) 216
decl_file (data1) struct_FILE.h (4)
decl_line (data1) 49
[ 47d4] member abbrev: 13
name (strp) "_flags"
type (ref4) [ 425e]
decl_file (data1) struct_FILE.h (4)
decl_line (data1) 51
data_member_location (data1) 0
[ 47e0] member abbrev: 13
name (strp) "_IO_read_ptr"
type (ref4) [ 4685]
decl_file (data1) struct_FILE.h (4)
decl_line (data1) 54
data_member_location (data1) 8
...
This information is useful because it allows you to verify that the library
that the caller is expecting has the same ABI as the function that the callee
is providing.
