I apologize if this is the wrong category.
I've built Swift from source, and was using only the REPL. Only now I found out swiftc fails to compile any program at all with message:
<unknown>:0: error: unable to execute command: <unknown>
Using swiftc to emit-lllvm though works fine.
Digging at the source-code, this error seems to be thrown in method runTaskQueueToCompletion of class PerformJobsState, file Compilation.cpp:
void runTaskQueueToCompletion() {
do {
using namespace std::placeholders;
// Ask the TaskQueue to execute.
if (TQ->execute(std::bind(&PerformJobsState::taskBegan, this, _1, _2),
std::bind(&PerformJobsState::taskFinished, this, _1, _2,
_3, _4, _5, _6),
std::bind(&PerformJobsState::taskSignalled, this, _1,
_2, _3, _4, _5, _6, _7))) {
if (Result == EXIT_SUCCESS) {
// FIXME: Error from task queue while Result == EXIT_SUCCESS most
// likely means some fork/exec or posix_spawn failed; TaskQueue saw
// "an error" at some stage before even calling us with a process
// exit / signal (or else a poll failed); unfortunately the task
// causing it was dropped on the floor and we have no way to recover
// it here, so we report a very poor, generic error.
Comp.getDiags().diagnose(SourceLoc(),
diag::error_unable_to_execute_command,
"<unknown>");
// ...
I tried rebuilding swift but I get the same error. I built it with the command:
utils/build-script --release-debuginfo --lldb --host-cc ~/Developer/llvm/build_9/bin/clang --host-cxx ~/Developer/llvm/build_9/bin/clang++
How can I fix this? Is there some something I should do in my OS to get the compiler to work?
More importantly, most people use one of the build presets to get all the relevant tools and libraries installed in a toolchain directory, rather than trying to construct a build-script invocation with a bunch of flags themselves. 