Fix for macOS symbol wrapping

Modules/app-module/CMakeLists.txt

@@ -12,14 +12,12 @@ tactility_add_module(app-module
     PRIV_REQUIRES TactilityKernelCpp
 )
 
-# Tells source/io.cpp its real-syscall fallback must go through __real_read/write/close()
+# Tells source/io.cpp its real-syscall fallback must go through __real_read/write/close() rather
-# rather than calling ::read/::write/::close() directly, on every platform whose build wraps
+# than calling ::read/::write/::close() directly, on every platform where those are wrapped: via
-# those symbols (ESP-IDF always; POSIX except macOS, whose linker doesn't support --wrap) -
+# -Wl,--wrap= on ESP-IDF and non-Apple POSIX (see Tactility/CMakeLists.txt and the top-level
-# see Tactility/CMakeLists.txt and the top-level CMakeLists.txt for where that's applied.
+# CMakeLists.txt), or via AppStdioWrap.cpp's dyld interpose on Apple (whose linker lacks --wrap).
-if (NOT APPLE)
+tactility_get_module_name(app-module MODULE_NAME)
-    tactility_get_module_name(app-module MODULE_NAME)
+target_compile_definitions(${MODULE_NAME} PRIVATE TT_APP_IO_WRAPS_STDIO)
-    target_compile_definitions(${MODULE_NAME} PRIVATE TT_APP_IO_WRAPS_STDIO)
-endif ()
 
 # install.cpp resolves an installed binary's fixed bin/<platform>/<binary>.so path itself, so it
 # needs the same platform-arch string app-posix-module's own CMakeLists.txt defines for its

Modules/app-module/tests/CMakeLists.txt

@@ -6,22 +6,20 @@ enable_language(C CXX ASM)
 file(GLOB_RECURSE TEST_SOURCES CONFIGURE_DEPENDS ${PROJECT_SOURCE_DIR}/source/*.cpp)
 add_executable(AppModuleTests EXCLUDE_FROM_ALL ${TEST_SOURCES})
 
-if (NOT APPLE)
+# Provides __wrap_read/write/close: paired with the -Wl,--wrap= below on non-Apple platforms (see
-    # Provides __wrap_read/write/close for the -Wl,--wrap= below (see Tactility/CMakeLists.txt
+# Tactility/CMakeLists.txt), or self-registered via dyld interpose on Apple (see the file itself).
-    # for the canonical pairing of this file with those flags).
+target_sources(AppModuleTests PRIVATE ${CMAKE_CURRENT_LIST_DIR}/../../../Tactility/Source/AppStdioWrap.cpp)
-    target_sources(AppModuleTests PRIVATE ${CMAKE_CURRENT_LIST_DIR}/../../../Tactility/Source/AppStdioWrap.cpp)
-endif ()
 
 target_include_directories(AppModuleTests PRIVATE ${DOCTESTINC} ${CMAKE_CURRENT_LIST_DIR}/../private)
 
 add_test(NAME AppModuleTests COMMAND AppModuleTests)
 
-# Matches app-module's own TT_APP_IO_WRAPS_STDIO (see Modules/app-module/CMakeLists.txt):
+# Matches app-module's own TT_APP_IO_WRAPS_STDIO (see Modules/app-module/CMakeLists.txt): io.cpp
-# io.cpp calls __real_read/write/close() on non-Apple POSIX, so any final link of it needs
+# calls __real_read/write/close() on every POSIX platform, so any final link of it needs these
-# these wraps too, or those symbols go unresolved. The printf-family/getc-family flags are
+# wraps too, or those symbols go unresolved. The printf-family/getc-family flags are needed for
-# needed for the same reason: AppStdioWrap.cpp compiles those __wrap_* functions unconditionally
+# the same reason: AppStdioWrap.cpp compiles those __wrap_* functions unconditionally on this
-# on this platform (see its own #if guard), and they reference __real_vfprintf/fputs/fputc/
+# platform, and they reference __real_vfprintf/fputs/fputc/fgetc/fgets. --wrap provides all of
-# fgetc/fgets - those only exist once the matching --wrap flag is passed.
+# these __real_* symbols on non-Apple; AppStdioWrap.cpp provides its own on Apple (see that file).
 if (NOT APPLE)
     target_link_options(AppModuleTests PRIVATE
         "-Wl,--wrap=read" "-Wl,--wrap=write" "-Wl,--wrap=close"

Platforms/platform-posix/source/pthread_stack_wrap.c

@@ -20,8 +20,15 @@ int __wrap_pthread_attr_setstack(pthread_attr_t* attr, void* stackaddr, size_t s
 }
 
 #ifdef __APPLE__
-#include <mach-o/dyld-interposing.h>
 
-DYLD_INTERPOSE(__wrap_pthread_attr_setstack, pthread_attr_setstack)
+// <mach-o/dyld-interposing.h> isn't a public SDK header (it ships with dyld's own source, not
+// Xcode/Command Line Tools), so this reimplements its DYLD_INTERPOSE macro locally.
+#define TT_DYLD_INTERPOSE(replacement, replacee) \
+    __attribute__((used)) static struct { const void* replacement; const void* replacee; } \
+        tt_interpose_##replacee __attribute__((section("__DATA,__interpose"))) = { \
+            (const void*)(unsigned long)&(replacement), (const void*)(unsigned long)&(replacee) \
+        };
+
+TT_DYLD_INTERPOSE(__wrap_pthread_attr_setstack, pthread_attr_setstack)
 
 #endif

Tactility/CMakeLists.txt

@@ -188,7 +188,8 @@ else ()
     # Routes every pthread_attr_setstack() call (FreeRTOS's POSIX port hands each task a stack
     # carved out of its own heap through this) to __wrap_pthread_attr_setstack() in
     # Platforms/platform-posix/source/pthread_stack_wrap.c, which no-ops it - see that file for why.
-    # --wrap is a GNU ld option; Apple's linker doesn't support it.
+    # --wrap is a GNU ld option; Apple's linker doesn't support it, so that file instead
+    # self-registers a dyld interpose for this symbol on Apple, needing no link flag here.
     if (NOT APPLE)
         target_link_options(Tactility PRIVATE "-Wl,--wrap=pthread_attr_setstack")
         # Routes every read()/write()/close() call to Tactility/Source/AppStdioWrap.cpp's
@@ -196,6 +197,7 @@ else ()
         # dispatch that lets an app's own stdio (e.g. a fileselection dialog's printf'd result
         # path) reach an AppStream a parent bound via app_manager_start_with_streams(). Mirrors
         # what ESP-IDF's build already does for the ESP32 target (see top-level CMakeLists.txt).
+        # On Apple, AppStdioWrap.cpp self-registers the same routing via dyld interpose instead.
         target_link_options(Tactility PRIVATE "-Wl,--wrap=read" "-Wl,--wrap=write" "-Wl,--wrap=close")
         # glibc's printf/fprintf/etc don't call the public write() symbol internally (they're
         # already compiled into libc.so, out of --wrap's reach), so the read/write/close wrap
@@ -203,7 +205,8 @@ else ()
         # wrappable syscall stubs - so this block is POSIX-only. Wrapping these symbols instead
         # redirects OUR OWN calls to them (the only ones --wrap can rewrite) through
         # AppStdioWrap.cpp's __wrap_* functions, which check the target stream (stdout/stdin) and
-        # fall back to the real libc function for any other FILE*.
+        # fall back to the real libc function for any other FILE*. Apple gets the same routing via
+        # dyld interpose, self-registered in that file - see its own #ifdef __APPLE__ block.
         target_link_options(Tactility PRIVATE
             "-Wl,--wrap=printf" "-Wl,--wrap=fprintf" "-Wl,--wrap=vprintf" "-Wl,--wrap=vfprintf"
             "-Wl,--wrap=puts" "-Wl,--wrap=fputs" "-Wl,--wrap=putchar" "-Wl,--wrap=fputc"

Tactility/Source/AppStdioWrap.cpp

@@ -1,9 +1,8 @@
 // SPDX-License-Identifier: Apache-2.0
 
-// Paired with -Wl,--wrap=read/write/close - see Tactility/CMakeLists.txt (POSIX) and the
+// Paired with -Wl,--wrap=read/write/close on POSIX (Tactility/CMakeLists.txt) and ESP32
-// top-level CMakeLists.txt (ESP32) for where that's applied. On a platform where it isn't
+// (top-level CMakeLists.txt); self-registered via dyld interpose below on Apple, whose linker
-// (currently: macOS, whose linker doesn't support --wrap), these are simply never called - real
+// doesn't support --wrap.
-// read()/write()/close() calls go straight through unredirected.
 #include <app/io.h>
 
 #include <sys/types.h>
@@ -24,21 +23,64 @@ int __wrap_close(int fd) {
 
 }
 
+#ifdef __APPLE__
+
+// --wrap also synthesizes __real_read/write/close automatically; dyld interpose doesn't, so
+// io.cpp's TT_APP_IO_WRAPS_STDIO fallback needs them defined here. dlsym(RTLD_NEXT, ...) is the
+// standard way to reach the true libSystem implementation despite the interpose below: a direct
+// call to read/write/close from this file would just recurse into __wrap_read/write/close, since
+// interpose rewrites every reference to those symbols in the process, this file included.
+#include <dlfcn.h>
+
+extern "C" {
+
+ssize_t __real_read(int fd, void* buffer, size_t size) {
+    static auto real = reinterpret_cast<ssize_t (*)(int, void*, size_t)>(dlsym(RTLD_NEXT, "read"));
+    return real(fd, buffer, size);
+}
+
+ssize_t __real_write(int fd, const void* buffer, size_t size) {
+    static auto real = reinterpret_cast<ssize_t (*)(int, const void*, size_t)>(dlsym(RTLD_NEXT, "write"));
+    return real(fd, buffer, size);
+}
+
+int __real_close(int fd) {
+    static auto real = reinterpret_cast<int (*)(int)>(dlsym(RTLD_NEXT, "close"));
+    return real(fd);
+}
+
+}
+
+// <mach-o/dyld-interposing.h> isn't a public SDK header (it ships with dyld's own source, not
+// Xcode/Command Line Tools), so this reimplements its DYLD_INTERPOSE macro locally; reused below
+// for the printf-family interposes too.
+#define TT_DYLD_INTERPOSE(replacement, replacee) \
+    __attribute__((used)) static struct { const void* replacement; const void* replacee; } \
+        tt_interpose_##replacee __attribute__((section("__DATA,__interpose"))) = { \
+            (const void*)(unsigned long)&(replacement), (const void*)(unsigned long)&(replacee) \
+        };
+
+TT_DYLD_INTERPOSE(__wrap_read, read)
+TT_DYLD_INTERPOSE(__wrap_write, write)
+TT_DYLD_INTERPOSE(__wrap_close, close)
+
+#endif // __APPLE__
+
 // region glibc stdio wraps
 //
-// glibc's printf/fprintf/etc are compiled into libc.so and call an internal, non-exported write()
+// libc's printf/fprintf/etc are compiled into the C library and call an internal, non-exported
-// alias - --wrap=write (above) can't reach that call, only calls WE make to the public symbol.
+// write() alias - --wrap=write/the read/write/close interpose above can't reach that call, only
-// These wraps instead redirect calls WE make to printf/fprintf/etc, the same trick as read/write/
+// calls WE make to the public symbol. These wraps instead redirect calls WE make to printf/
-// close above. Newlib (ESP-IDF) doesn't have this gap - its stdio does call the wrappable syscall
+// fprintf/etc, the same trick as read/write/close above. Newlib (ESP-IDF) doesn't have this gap -
-// stubs - so Tactility/CMakeLists.txt only applies the matching -Wl,--wrap= flags on POSIX.
+// its stdio does call the wrappable syscall stubs - so this block is POSIX-only.
 //
 // Scoped to the printf/getc families only: fread/fwrite take an arbitrary FILE* and are already
 // used sitewide for real file I/O (e.g. File.cpp's readBinaryInternal), so wrapping them would
 // route every such call through this file's stdin/stdout check - a correctness risk for unrelated
-// code that isn't worth taking here. putc/getc are excluded too since glibc defines them as
+// code that isn't worth taking here. putc/getc are excluded too since libc defines them as
 // macros, not real calls, so wrapping those symbols wouldn't reliably intercept them.
 
-#if !defined(ESP_PLATFORM) && !defined(__APPLE__)
+#if !defined(ESP_PLATFORM)
 
 #include <cstdarg>
 #include <cstdio>
@@ -54,6 +96,43 @@ int __real_fgetc(FILE* stream);
 char* __real_fgets(char* buffer, int size, FILE* stream);
 }
 
+#ifdef __APPLE__
+
+// --wrap synthesizes these automatically elsewhere; on Apple they're defined here via
+// dlsym(RTLD_NEXT, ...) instead - see the read/write/close __real_* block above for why.
+#include <dlfcn.h>
+
+extern "C" {
+
+int __real_vfprintf(FILE* stream, const char* format, va_list args) {
+    static auto real = reinterpret_cast<int (*)(FILE*, const char*, va_list)>(dlsym(RTLD_NEXT, "vfprintf"));
+    return real(stream, format, args);
+}
+
+int __real_fputs(const char* s, FILE* stream) {
+    static auto real = reinterpret_cast<int (*)(const char*, FILE*)>(dlsym(RTLD_NEXT, "fputs"));
+    return real(s, stream);
+}
+
+int __real_fputc(int c, FILE* stream) {
+    static auto real = reinterpret_cast<int (*)(int, FILE*)>(dlsym(RTLD_NEXT, "fputc"));
+    return real(c, stream);
+}
+
+int __real_fgetc(FILE* stream) {
+    static auto real = reinterpret_cast<int (*)(FILE*)>(dlsym(RTLD_NEXT, "fgetc"));
+    return real(stream);
+}
+
+char* __real_fgets(char* buffer, int size, FILE* stream) {
+    static auto real = reinterpret_cast<char* (*)(char*, int, FILE*)>(dlsym(RTLD_NEXT, "fgets"));
+    return real(buffer, size, stream);
+}
+
+}
+
+#endif // __APPLE__
+
 namespace {
 
 void writeAllToStdout(const void* data, size_t size) {
@@ -195,6 +274,20 @@ char* __wrap_fgets(char* buffer, int size, FILE* stream) {
 
 }
 
-#endif // !ESP_PLATFORM && !__APPLE__
+#ifdef __APPLE__
+TT_DYLD_INTERPOSE(__wrap_vprintf, vprintf)
+TT_DYLD_INTERPOSE(__wrap_printf, printf)
+TT_DYLD_INTERPOSE(__wrap_vfprintf, vfprintf)
+TT_DYLD_INTERPOSE(__wrap_fprintf, fprintf)
+TT_DYLD_INTERPOSE(__wrap_puts, puts)
+TT_DYLD_INTERPOSE(__wrap_fputs, fputs)
+TT_DYLD_INTERPOSE(__wrap_putchar, putchar)
+TT_DYLD_INTERPOSE(__wrap_fputc, fputc)
+TT_DYLD_INTERPOSE(__wrap_getchar, getchar)
+TT_DYLD_INTERPOSE(__wrap_fgetc, fgetc)
+TT_DYLD_INTERPOSE(__wrap_fgets, fgets)
+#endif // __APPLE__
+
+#endif // !ESP_PLATFORM
 
 // endregion

Tactility/Tests/CMakeLists.txt

@@ -20,9 +20,10 @@ target_include_directories(TactilityTests PRIVATE ${CMAKE_CURRENT_LIST_DIR}/../P
 add_test(NAME TactilityTests COMMAND TactilityTests)
 
 # Matches Tactility/CMakeLists.txt's own set of --wrap flags: this binary also compiles
-# AppStdioWrap.cpp and links app-module (whose io.cpp calls __real_read/write/close() on
+# AppStdioWrap.cpp and links app-module (whose io.cpp calls __real_read/write/close() on every
-# non-Apple POSIX - see TT_APP_IO_WRAPS_STDIO in Modules/app-module/CMakeLists.txt), so it
+# POSIX platform - see TT_APP_IO_WRAPS_STDIO in Modules/app-module/CMakeLists.txt), so it needs
-# needs the same wraps applied or those go unresolved.
+# the same wraps applied on non-Apple, or those go unresolved; AppStdioWrap.cpp provides its own
+# on Apple via dyld interpose (see that file).
 if (NOT APPLE)
     target_link_options(TactilityTests PRIVATE
         "-Wl,--wrap=pthread_attr_setstack" "-Wl,--wrap=read" "-Wl,--wrap=write" "-Wl,--wrap=close"