https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110976
Bug ID: 110976
Summary: Cryptic error message when incorrectly dereferencing a
pointer in an anonymous union
Product: gcc
Version: 14.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: jesper.oqvist at gmail dot com
Target Milestone: ---
The following program gives me a cryptic error message when compiled with GCC
14 snapshot 20230806:
struct S { union { struct S* x; }; };
struct S* f(struct S s)
{
return s.x.x;
}
Compiling this program with $HOME/opt/gcc-14/bin/gcc anon_union.c gives the
error message below:
anon_union.c: In function 'f':
anon_union.c:4:13: error: 's.<U27b8>.x' is a pointer; did you mean to use '->'?
4 | return s.x.x;
| ^
| ->
I presume the <U27b8> part is how GCC names the anonymous union in struct S,
but it seems like this could be formatted a bit nicer to make the error message
easier to understand. Each time I re-run the compiler on the same program the
part in angle brackets changes to another 5-letter string starting with U.
Below is the gcc -v output:
$HOME/opt/gcc-14/bin/gcc -v anon_union.c
Using built-in specs.
COLLECT_GCC=/home/jesper/opt/gcc-14/bin/gcc
COLLECT_LTO_WRAPPER=/home/jesper/opt/gcc-14/libexec/gcc/x86_64-pc-linux-gnu/14.0.0/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: ../gcc-14-20230806/configure --prefix=/home/jesper/opt/gcc-14
--disable-nls --disable-werror --disable-bootstrap --enable-languages=c,c++
Thread model: posix
Supported LTO compression algorithms: zlib
gcc version 14.0.0 20230806 (experimental) (GCC)
COLLECT_GCC_OPTIONS='-v' '-mtune=generic' '-march=x86-64' '-dumpdir' 'a-'
/home/jesper/opt/gcc-14/libexec/gcc/x86_64-pc-linux-gnu/14.0.0/cc1 -quiet -v
-imultiarch x86_64-linux-gnu anon_union.c -quiet -dumpdir a- -dumpbase
anon_union.c -dumpbase-ext .c -mtune=generic -march=x86-64 -version -o
/tmp/ccsUEV7J.s
GNU C17 (GCC) version 14.0.0 20230806 (experimental) (x86_64-pc-linux-gnu)
compiled by GNU C version 11.4.0, GMP version 6.2.1, MPFR version
4.1.0, MPC version 1.2.1, isl version isl-0.24-GMP
GGC heuristics: --param ggc-min-expand=30 --param ggc-min-heapsize=4096
ignoring nonexistent directory "/usr/local/include/x86_64-linux-gnu"
ignoring nonexistent directory
"/home/jesper/opt/gcc-14/lib/gcc/x86_64-pc-linux-gnu/14.0.0/../../../../x86_64-pc-linux-gnu/include"
#include "..." search starts here:
#include <...> search starts here:
/home/jesper/opt/gcc-14/lib/gcc/x86_64-pc-linux-gnu/14.0.0/include
/usr/local/include
/home/jesper/opt/gcc-14/include
/home/jesper/opt/gcc-14/lib/gcc/x86_64-pc-linux-gnu/14.0.0/include-fixed/x86_64-linux-gnu
/home/jesper/opt/gcc-14/lib/gcc/x86_64-pc-linux-gnu/14.0.0/include-fixed
/usr/include/x86_64-linux-gnu
/usr/include
End of search list.
Compiler executable checksum: 020a05d35e6345424c620c1d2d7de9eb
