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Fix building where posix_spawn_file_actions_addchdir_np is unavailable #104

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Merged
sheredom merged 3 commits into from
Aug 9, 2026
Merged

Fix building where posix_spawn_file_actions_addchdir_np is unavailable #104

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fd48c47
Fix building against glibc older than 2.29
bernardladenthin Aug 1, 2026
620ce44
Allow overriding SUBPROCESS_HAVE_CWD and document it
bernardladenthin Aug 1, 2026
6900aed
Fix building against macOS older than 10.15
bernardladenthin Aug 7, 2026
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7 changes: 7 additions & 0 deletions README.md
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Original file line number Diff line number Diff line change
Expand Up @@ -179,6 +179,13 @@ pass `NULL` to inherit the parent's current working directory. On Windows,
custom environment entries and the current working directory string are
interpreted as UTF-8.

Not every platform can honour a custom working directory. Where it cannot,
`SUBPROCESS_HAVE_CWD` is defined to `0` and passing a non-`NULL` working
directory fails with `ENOSYS`; this currently affects glibc older than 2.29,
macOS older than 10.15, and iOS, tvOS and watchOS, where Apple marks the
underlying call unavailable. Define `SUBPROCESS_HAVE_CWD` yourself to override
the detection, for instance on musl older than 1.1.24.

Note though that you **cannot** specify `subprocess_option_inherit_environment`
with a custom environment. If you want to merge some custom environment with the
parent process environment then it is up to you as the user to query the original
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21 changes: 21 additions & 0 deletions subprocess.h
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Expand Up @@ -274,6 +274,25 @@ subprocess_weak int subprocess_alive(struct subprocess_s *const process);
#include <unistd.h>
#endif

/* Whether subprocess_create_ex can honour process_cwd. glibc only gained
posix_spawn_file_actions_addchdir_np in 2.29, and macOS in 10.15; the SDKs
mark it unavailable on iOS, tvOS and watchOS, where the undefined version
macro folds to 0 and so answers correctly. Define this yourself to override
the detection, for instance on musl older than 1.1.24. */
#if !defined(SUBPROCESS_HAVE_CWD)

@sheredom sheredom Aug 9, 2026

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We don't need this new define - just add it inline where you set ENOSYS.

@sheredom sheredom Aug 9, 2026

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Changed my mind actually - you are right to add the define for the testing too. I generally dislike defines s'all!

#if defined(__GLIBC__)
#if __GLIBC_PREREQ(2, 29)
#define SUBPROCESS_HAVE_CWD 1
#else
#define SUBPROCESS_HAVE_CWD 0
#endif
#elif defined(__APPLE__) && MAC_OS_X_VERSION_MIN_REQUIRED < 101500
#define SUBPROCESS_HAVE_CWD 0
#else
#define SUBPROCESS_HAVE_CWD 1
#endif
#endif

#if defined(_WIN32)

#include <wchar.h>
Expand Down Expand Up @@ -1207,6 +1226,8 @@ int subprocess_create_ex(const char *const commandLine[], int options,
if (process_cwd) {
#if defined(__APPLE__) && MAC_OS_X_VERSION_MIN_REQUIRED >= 260000
posix_error = posix_spawn_file_actions_addchdir(&actions, process_cwd);
#elif !SUBPROCESS_HAVE_CWD
posix_error = ENOSYS;
#else
#if defined(__APPLE__) && defined(__clang__)
#pragma clang diagnostic push
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2 changes: 2 additions & 0 deletions test/test_shared.h
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Expand Up @@ -1116,6 +1116,7 @@ SUBPROCESS_TEST(environment, specify_environment) {
ASSERT_EQ(0, subprocess_destroy(&process));
}

#if SUBPROCESS_HAVE_CWD
SUBPROCESS_TEST(create_ex, subprocess_cwd) {
char current_path[4096];
char target_path[4096];
Expand Down Expand Up @@ -1156,6 +1157,7 @@ SUBPROCESS_TEST(create_ex, subprocess_cwd) {

ASSERT_EQ(0, subprocess_destroy(&process));
}
#endif

#if !defined(_MSC_VER)
SUBPROCESS_TEST(executable_resolve, no_slashes_with_environment) {
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