******************************************************************************* The compiler produces an internal error during the tsubst_lambda_expr when compiling the provided code with the specified options. The issue can also be reproduced on Compiler Explorer. ******************************************************************************* OS and Platform: # uname -a Linux ubuntu 4.15.0-213-generic #224-Ubuntu SMP Mon Jun 19 13:30:12 UTC 2023 x86_64 x86_64 x86_64 GNU/Linux ******************************************************************************* # g++ -v Using built-in specs. COLLECT_GCC=g++ COLLECT_LTO_WRAPPER=/root/gdbtest/gcc/gcc-15/libexec/gcc/x86_64-pc-linux-gnu/15.0.0/lto-wrapper Target: x86_64-pc-linux-gnu Configured with: /root/gdbtest/gcc/obj/../gcc/configure --prefix=/root/gdbtest/gcc/gcc-15 --enable-languages=c,c++,fortran,go --disable-multilib Thread model: posix Supported LTO compression algorithms: zlib gcc version 15.0.0 20240509 (experimental) (GCC) ******************************************************************************* Program: # cat t.c template <int N> int f (int n) { int x[1][n]; return [x[0]] /* () { return 0; } */; } int i = f<1>(1); ******************************************************************************* Command Lines: # g++ t.c -flto -fwhole-program -g -gdwarf-4 -ggdb3 -grecord-gcc-switches -fanalyzer -fdump-analyzer -Wno-analyzer-nul l-dereference -Wno-analyzer-use-after-free -c -o t.o t.c: In function ‘int f(int)’: t.c:6:12: error: expected ‘,’ before ‘[’ token 6 | return [x[0]] /* () { return 0; } */; | ^ | , t.c:6:12: error: expected identifier before ‘[’ token t.c: In lambda function: t.c:6:39: error: expected ‘{’ before ‘;’ token 6 | return [x[0]] /* () { return 0; } */; | ^ t.c: In instantiation of ‘int f(int) [with int N = 1]’: t.c:9:13: required from here 9 | int i = f<1>(1); | ~~~~^~~ t.c:6:10: sorry, unimplemented: capture of variably-modified type ‘int [1][n]’ that is not an N3639 array of runtime bound 6 | return [x[0]] /* () { return 0; } */; | ^~~~~~ t.c:6:10: note: because the array element type ‘int [n]’ has variable size t.c:6:15: internal compiler error: in tsubst_stmt, at cp/pt.cc:18514 6 | return [x[0]] /* () { return 0; } */; | ^ 0x8308a0 tsubst_stmt /root/gdbtest/gcc/obj/../gcc/gcc/cp/pt.cc:18514 0xce1718 tsubst_stmt /root/gdbtest/gcc/obj/../gcc/gcc/cp/pt.cc:18410 0xce1718 tsubst_lambda_expr(tree_node*, tree_node*, int, tree_node*) /root/gdbtest/gcc/obj/../gcc/gcc/cp/pt.cc:19850 0xcbe1a0 tsubst_expr(tree_node*, tree_node*, int, tree_node*) /root/gdbtest/gcc/obj/../gcc/gcc/cp/pt.cc:21757 0xcc4837 tsubst_stmt /root/gdbtest/gcc/obj/../gcc/gcc/cp/pt.cc:19482 0xcc6446 tsubst_stmt /root/gdbtest/gcc/obj/../gcc/gcc/cp/pt.cc:18434 0xcc6106 tsubst_stmt /root/gdbtest/gcc/obj/../gcc/gcc/cp/pt.cc:18410 0xcc6106 tsubst_stmt /root/gdbtest/gcc/obj/../gcc/gcc/cp/pt.cc:18424 0xcc6bee tsubst_stmt /root/gdbtest/gcc/obj/../gcc/gcc/cp/pt.cc:18797 0xce0b52 tsubst_stmt /root/gdbtest/gcc/obj/../gcc/gcc/cp/pt.cc:18410 0xce0b52 instantiate_body /root/gdbtest/gcc/obj/../gcc/gcc/cp/pt.cc:27107 0xcc4425 instantiate_decl(tree_node*, bool, bool) /root/gdbtest/gcc/obj/../gcc/gcc/cp/pt.cc:27392 0xcf0c4b instantiate_pending_templates(int) /root/gdbtest/gcc/obj/../gcc/gcc/cp/pt.cc:27468 0xb8cc67 c_parse_final_cleanups() /root/gdbtest/gcc/obj/../gcc/gcc/cp/decl2.cc:5195 0xddf3a0 c_common_parse_file() /root/gdbtest/gcc/obj/../gcc/gcc/c-family/c-opts.cc:1329 Please submit a full bug report, with preprocessed source (by using -freport-bug). Please include the complete backtrace with any bug report. See <https://gcc.gnu.org/bugs/> for instructions. ******************************************************************************* Also ICE on trunk, compiler explorer:https://godbolt.org/z/4j14rxbfr *******************************************************************************