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Synchronize child_process updates using interlocked Win32 APIs

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This commit is contained in:
Andrea Mazzoleni 2026-07-06 17:37:53 +02:00
parent 4bbfdc43d9
commit 5edf0b2c03
1 changed files with 24 additions and 4 deletions
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28
cmdline/main.c
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@ -103,13 +103,33 @@ static char* argutf8(const WCHAR* arg)
}
/* Global variable to store child process handle */
static HANDLE child_process = NULL;
static void* volatile child_process = NULL;
/*
* Safe atomic access helpers for child_process.
*
* The console_handler runs concurrently on an OS-managed thread created by
* the Windows kernel. Because plain writes and standard volatile access do not
* guarantee CPU cache visibility (flushing from store buffers) or prevent CPU/compiler
* out-of-order reordering (due to lack of hardware memory barriers/fences on MinGW),
* we must use Win32 Interlocked APIs to ensure safe, atomic, fence-protected reads
* and writes of the child process handle.
*/
static HANDLE child_process_read(void)
{
return InterlockedCompareExchangePointer(&child_process, NULL, NULL);
}
static void child_process_write(HANDLE handle)
{
InterlockedExchangePointer(&child_process, handle);
}
/* Console control handler - forwards Ctrl+C, Ctrl+Break to child */
static BOOL WINAPI console_handler(DWORD ctrl_type)
{
/* if no child, default behavior */
if (child_process == NULL)
if (child_process_read() == NULL)
return FALSE;
switch (ctrl_type) {
@ -225,7 +245,7 @@ int main(int argc, char* argv[])
}
/* store child process handle for signal handler */
child_process = pi.hProcess;
child_process_write(pi.hProcess);
wait = WaitForSingleObject(pi.hProcess, INFINITE);
if (wait != WAIT_OBJECT_0) {
@ -237,7 +257,7 @@ int main(int argc, char* argv[])
}
/* clear child process handle */
child_process = NULL;
child_process_write(NULL);
if (!GetExitCodeProcess(pi.hProcess, &res)) {
fprintf(stderr, "GetExitCodeProcess failed: %lu\n", (unsigned long)GetLastError());