Fix SystemNative_IsATty P/Invoke missing on iOS/tvOS/MacCatalyst by Copilot · Pull Request #126302 · dotnet/runtime

Copilot · 2026-03-30T10:22:33Z

System.Diagnostics.Process has a P/Invoke to SystemNative_IsATty, but that symbol is not exported by libSystem.Native on iOS, tvOS, and Mac Catalyst, causing a runtime failure on those platforms.

Description

Guard SystemNative_IsATty in pal_console.c to unconditionally return 0 on TARGET_IOS, TARGET_TVOS, and TARGET_MACCATALYST — there is no terminal on these platforms.

int32_t SystemNative_IsATty(intptr_t fd)
{
#if defined(TARGET_MACCATALYST) || defined(TARGET_IOS) || defined(TARGET_TVOS)
    // there is no terminal on these platforms
    (void)fd;
    return 0;
#else
    return isatty(ToFileDescriptor(fd));
#endif
}

This follows the same #if defined(TARGET_MACCATALYST) || defined(TARGET_IOS) || defined(TARGET_TVOS) guard pattern used elsewhere in the native libs (e.g., pal_icushim_static.c, pal_x509.c).

fixes #126299

… calling isatty Agent-Logs-Url: https://github.com/dotnet/runtime/sessions/96c22fac-0eb4-4756-ae91-390e30c5c572 Co-authored-by: adamsitnik <6011991+adamsitnik@users.noreply.github.com>

src/native/libs/System.Native/pal_console.c

Agent-Logs-Url: https://github.com/dotnet/runtime/sessions/715fb05b-348a-414e-9529-e30e3eacbbbb Co-authored-by: adamsitnik <6011991+adamsitnik@users.noreply.github.com>

adamsitnik

LGTM!

dotnet-policy-service · 2026-03-30T10:35:56Z

Tagging subscribers to this area: @dotnet/area-system-diagnostics-process
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Copilot

Pull request overview

Fixes a runtime P/Invoke failure on iOS/tvOS/MacCatalyst by ensuring SystemNative_IsATty is always present in libSystem.Native, while returning a consistent “not a TTY” result on platforms where TTY semantics don’t apply.

Changes:

Add an Apple mobile/Catalyst preprocessor guard to SystemNative_IsATty.
On TARGET_IOS, TARGET_TVOS, and TARGET_MACCATALYST, return 0 without calling isatty.

adamsitnik · 2026-03-30T10:39:13Z

src/native/libs/System.Native/pal_console.c


 int32_t SystemNative_IsATty(intptr_t fd)
 {
+#if defined(TARGET_MACCATALYST) || defined(TARGET_IOS) || defined(TARGET_TVOS)


@rolfbjarne is this the correct fix? or is pal_console.c not compiled for iOS family because there is simply no terminal there?

@rolfbjarne is this the correct fix? or is pal_console.c not compiled for iOS family because there is simply no terminal there?

It pulls in pal_log.m instead (the .c is only included on macOS):

runtime/src/native/libs/System.Native/CMakeLists.txt

Lines 68 to 94 in 7c91160

if (CLR_CMAKE_TARGET_APPLE)

list (APPEND NATIVE_SOURCES_OBJC_NO_ARC

pal_autoreleasepool.m

pal_environment.m

pal_searchpath.m

pal_datetime.m)

if (CLR_CMAKE_TARGET_MACCATALYST OR CLR_CMAKE_TARGET_IOS OR CLR_CMAKE_TARGET_TVOS)

list (APPEND NATIVE_SOURCES_OBJC_NO_ARC pal_log.m)

if (CLR_CMAKE_TARGET_MACCATALYST)

list (APPEND NATIVE_SOURCES_OBJC_NO_ARC pal_iossupportversion.m)

else()

list (APPEND NATIVE_SOURCES pal_iossupportversion.c)

endif ()

elseif (CLR_CMAKE_TARGET_OSX)

list (APPEND NATIVE_SOURCES

pal_console.c

pal_log.c

pal_iossupportversion.c)

else()

message(FATAL_ERROR "Unsupported Apple platform")

endif ()

set_source_files_properties(${NATIVE_SOURCES_OBJC_NO_ARC} PROPERTIES COMPILE_FLAGS "-fno-objc-arc ${CLR_CMAKE_COMMON_OBJC_FLAGS}")

list (APPEND NATIVE_SOURCES ${NATIVE_SOURCES_OBJC_NO_ARC})

else()

The ConsolePal.iOS.cs is pretty barebones, I would look why the p/invoke is even included instead of trying to stub out.

verify-entrypoints.sh was supposed to catch this, but we haven't turned it on for mobile. would be nice to fix that

I've also opened #126305 to ensure I don't break any mobile platforms again (I already added tests for Android to avoid that, but missed the catalyst vs ios difference)

Oh the reference is from Process? Out of curiosity I had a look and...

runtime/src/libraries/System.Diagnostics.Process/src/System/Diagnostics/Process.Unix.cs

Lines 363 to 392 in 36e6179

if (PlatformDoesNotSupportProcessStartAndKill)

{

throw new PlatformNotSupportedException();

}

EnsureInitialized();

string? filename;

string[] argv;

IDictionary<string, string?> env = startInfo.Environment;

string? cwd = !string.IsNullOrWhiteSpace(startInfo.WorkingDirectory) ? startInfo.WorkingDirectory : null;

bool setCredentials = !string.IsNullOrEmpty(startInfo.UserName);

uint userId = 0;

uint groupId = 0;

uint[]? groups = null;

if (setCredentials)

{

(userId, groupId, groups) = GetUserAndGroupIds(startInfo);

}

// .NET applications don't echo characters unless there is a Console.Read operation.

// Unix applications expect the terminal to be in an echoing state by default.

// To support processes that interact with the terminal (e.g. 'vi'), we need to configure the

// terminal to echo. We keep this configuration as long as there are children possibly using the terminal.

// Handle can be null only for UseShellExecute or platforms that don't support Console.Open* methods like Android.

bool usesTerminal = (stdinHandle is not null && Interop.Sys.IsATty(stdinHandle))

|| (stdoutHandle is not null && Interop.Sys.IsATty(stdoutHandle))

|| (stderrHandle is not null && Interop.Sys.IsATty(stderrHandle));

The PlatformDoesNotSupportProcessStartAndKill at the beginning is exactly iDevices. So this should all be unreachable.

System.Diagnostic.Process already multitargets, and it already did multitarget when people added the if check. Weird. This feels like something that should be a partial class.

The PlatformDoesNotSupportProcessStartAndKill at the beginning is exactly iDevices. So this should all be unreachable.

But Process is supported on mac catalyst and not supported on iOS and tvOS:

runtime/src/libraries/System.Diagnostics.Process/src/System/Diagnostics/Process.Unix.cs

Line 993 in 508f440

=> (OperatingSystem.IsIOS() && !OperatingSystem.IsMacCatalyst()) || OperatingSystem.IsTvOS();

FWIW we could support it on iOS with my most recent changes (I think: #126097 (comment))

This feels like something that should be a partial class.

Let's say there is a place for improvement and I am trying really hard to make it happen right now ;P

rolfbjarne

I'm not sure I understand how this is going to fix anything, because only changing SystemNative_IsATty doesn't do anything because SystemNative_IsATty isn't built for these platforms in the first place.

rolfbjarne · 2026-03-30T13:01:09Z

src/native/libs/System.Native/pal_console.c

 int32_t SystemNative_IsATty(intptr_t fd)
 {
+#if defined(TARGET_MACCATALYST) || defined(TARGET_IOS) || defined(TARGET_TVOS)
+    // there is no terminal on these platforms


There's a terminal on Mac Catalyst (but none on iOS or tvOS).

adamsitnik · 2026-03-30T13:10:56Z

I'm not sure I understand how this is going to fix anything, because only changing SystemNative_IsATty doesn't do anything because SystemNative_IsATty isn't built for these platforms in the first place.

You are right, it's not going to fix the problem and that is why I've asked you to review this PR (#126302 (comment)) as I have no clue about mobile targets

adamsitnik · 2026-03-30T13:12:08Z

Let's get the tests at least failing first in #126306

Initial plan

8971f87

Copilot AI assigned Copilot and adamsitnik Mar 30, 2026

Copilot started work on behalf of adamsitnik March 30, 2026 10:22 View session

Copilot AI linked an issue Mar 30, 2026 that may be closed by this pull request

Apple mobile: System.Diagnostics.Process.dll has P/Invoke to SystemNative_IsATty which doesn't exist #126299

Open

Fix SystemNative_IsATty for iOS/tvOS/MacCatalyst: return 0 instead of…

06b2044

… calling isatty Agent-Logs-Url: https://github.com/dotnet/runtime/sessions/96c22fac-0eb4-4756-ae91-390e30c5c572 Co-authored-by: adamsitnik <6011991+adamsitnik@users.noreply.github.com>

Copilot AI changed the title ~~[WIP] Fix P/Invoke for SystemNative_IsATty in Process.dll~~ Fix SystemNative_IsATty P/Invoke missing on iOS/tvOS/MacCatalyst Mar 30, 2026

Copilot finished work on behalf of adamsitnik March 30, 2026 10:26

Copilot AI requested a review from adamsitnik March 30, 2026 10:26

adamsitnik reviewed Mar 30, 2026

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src/native/libs/System.Native/pal_console.c Outdated Show resolved Hide resolved

Copilot started work on behalf of adamsitnik March 30, 2026 10:29 View session

Improve comment: there is no terminal on iOS/tvOS/MacCatalyst

e35c251

Agent-Logs-Url: https://github.com/dotnet/runtime/sessions/715fb05b-348a-414e-9529-e30e3eacbbbb Co-authored-by: adamsitnik <6011991+adamsitnik@users.noreply.github.com>

adamsitnik marked this pull request as ready for review March 30, 2026 10:34

Copilot AI review requested due to automatic review settings March 30, 2026 10:34

adamsitnik approved these changes Mar 30, 2026

View reviewed changes

Copilot finished work on behalf of adamsitnik March 30, 2026 10:34

Copilot AI requested a review from adamsitnik March 30, 2026 10:34

adamsitnik requested a review from rolfbjarne March 30, 2026 10:34

adamsitnik added this to the 11.0.0 milestone Mar 30, 2026

adamsitnik added os-ios Apple iOS os-tvos Apple tvOS labels Mar 30, 2026

Copilot started reviewing on behalf of adamsitnik March 30, 2026 10:35 View session

adamsitnik added the area-System.Diagnostics.Process label Mar 30, 2026

Copilot AI reviewed Mar 30, 2026

View reviewed changes

adamsitnik reviewed Mar 30, 2026

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rolfbjarne reviewed Mar 30, 2026

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adamsitnik closed this Mar 30, 2026

adamsitnik deleted the copilot/fix-pinvoke-to-systemnative-isatty branch March 30, 2026 13:12

This was referenced Mar 30, 2026

Unable to pull image from mcr.microsoft.com #117164

Open

XHarness package install failure on iOS due to devicectl NSPOSIXErrorDomain error 49 #123796

Open

Android arm32 device not found (armeabi-v7a architecture unavailable) #125440

Open

	if (CLR_CMAKE_TARGET_APPLE)
	list (APPEND NATIVE_SOURCES_OBJC_NO_ARC
	pal_autoreleasepool.m
	pal_environment.m
	pal_searchpath.m
	pal_datetime.m)

	if (CLR_CMAKE_TARGET_MACCATALYST OR CLR_CMAKE_TARGET_IOS OR CLR_CMAKE_TARGET_TVOS)
	list (APPEND NATIVE_SOURCES_OBJC_NO_ARC pal_log.m)

	if (CLR_CMAKE_TARGET_MACCATALYST)
	list (APPEND NATIVE_SOURCES_OBJC_NO_ARC pal_iossupportversion.m)
	else()
	list (APPEND NATIVE_SOURCES pal_iossupportversion.c)
	endif ()
	elseif (CLR_CMAKE_TARGET_OSX)
	list (APPEND NATIVE_SOURCES
	pal_console.c
	pal_log.c
	pal_iossupportversion.c)
	else()
	message(FATAL_ERROR "Unsupported Apple platform")
	endif ()

	set_source_files_properties(${NATIVE_SOURCES_OBJC_NO_ARC} PROPERTIES COMPILE_FLAGS "-fno-objc-arc ${CLR_CMAKE_COMMON_OBJC_FLAGS}")
	list (APPEND NATIVE_SOURCES ${NATIVE_SOURCES_OBJC_NO_ARC})
	else()

	if (PlatformDoesNotSupportProcessStartAndKill)
	{
	throw new PlatformNotSupportedException();
	}

	EnsureInitialized();

	string? filename;
	string[] argv;

	IDictionary<string, string?> env = startInfo.Environment;
	string? cwd = !string.IsNullOrWhiteSpace(startInfo.WorkingDirectory) ? startInfo.WorkingDirectory : null;

	bool setCredentials = !string.IsNullOrEmpty(startInfo.UserName);
	uint userId = 0;
	uint groupId = 0;
	uint[]? groups = null;
	if (setCredentials)
	{
	(userId, groupId, groups) = GetUserAndGroupIds(startInfo);
	}

	// .NET applications don't echo characters unless there is a Console.Read operation.
	// Unix applications expect the terminal to be in an echoing state by default.
	// To support processes that interact with the terminal (e.g. 'vi'), we need to configure the
	// terminal to echo. We keep this configuration as long as there are children possibly using the terminal.
	// Handle can be null only for UseShellExecute or platforms that don't support Console.Open* methods like Android.
	bool usesTerminal = (stdinHandle is not null && Interop.Sys.IsATty(stdinHandle))
	\|\| (stdoutHandle is not null && Interop.Sys.IsATty(stdoutHandle))
	\|\| (stderrHandle is not null && Interop.Sys.IsATty(stderrHandle));

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Copilot AI commented Mar 30, 2026 •

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