The use and error reporting on nested { } in inline asm


With this piece of code:
// inlbra2.c
void foo() { __asm__("#{{[a-zA-Z]}}":::"memory"); }
int main(void) { return 0; }

We crash with the following:
$ ~/INSTALLS/clang+llvm-3.9.0-x86_64-fedora23/bin/clang -S -o- inbra2.c
        .file "inbra2.c"
        .globl foo
        .p2align 4, 0x90
        .type foo,@function
foo: # @foo
# BB#0:
        pushq %rbp
        .cfi_def_cfa_offset 16
        .cfi_offset %rbp, -16
        movq %rsp, %rbp
        .cfi_def_cfa_register %rbp
fatal error: error in backend: Nested variants found in inline asm
string: '#$($([a-zA-Z]$)$)'
clang-3.9: error: clang frontend command failed with exit code 70 (use
-v to see invocation)
clang version 3.9.0 (tags/RELEASE_390/final)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /home/pmatos/INSTALLS/clang+llvm-3.9.0-x86_64-fedora23/bin
clang-3.9: note: diagnostic msg: PLEASE submit a bug report to and include the crash backtrace, preprocessed
source, and associated run script.
clang-3.9: note: diagnostic msg: