libcxxabi contains the runtime support for C++.  But, as some folks have 
realized, it is not complete.  It relies on some _Unwind_* functions to be
supplied by the OS. That means it cannot be ported to platforms that don’t 
already have an unwinder.  

Years ago Apple wrote its own unwinder for MacOSX and iOS.  To make libcxxabi 
complete, Apple has decided the source code for its unwinder can be contributed
to the open source LLVM libcxxabi project, with a dual licensed under LLVM 
and MIT license.

So, I’ve spent some time cleaning up the sources to make them conform with 
LLVM style and to conditionalize the sources in a way that should make it 
easier to port to other platforms.  The sources are in a separate "Unwind" 
directory under "src" in libcxxabi.  

Background:
Most architectures now use "zero cost" exceptions for C++.  The zero cost means
there are no extra instructions executed if no exceptions are thrown.  But if 
an exception is thrown, the runtime must consult side tables and figure out how
to restore registers and "unwind" from the current stack frame to the catch 
clause.  That ability to modify the stack frames and cause the thread to resume 
in a catch clause with all registers restored properly is the main purpose 
of the unwinder.

This unwinder has two levels of API.  The high level APIs are the _Unwind_* 
functions which the cxa_* exception functions in libcxxabi require.  The low 
level APIs are the unw_* functions which are an interface defined by the the 
old HP libunwind project (which shares no code with this unwinder).

llvm-svn: 192136

Author: Nick Kledzik

libcxxabi/include/libunwind.h

@@ -0,0 +1,356 @@
+//===---------------------------- libunwind.h -----------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//
+// Compatible with libuwind API documented at:
+//   http://www.nongnu.org/libunwind/man/libunwind(3).html
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef __LIBUNWIND__
+#define __LIBUNWIND__
+
+#include <stdint.h>
+#include <stddef.h>
+
+#if __APPLE__
+  #include <Availability.h>
+    #if __arm__
+       #define LIBUNWIND_AVAIL __attribute__((unavailable))
+    #else
+      #define LIBUNWIND_AVAIL __OSX_AVAILABLE_STARTING(__MAC_10_6, __IPHONE_5_0)
+    #endif
+#else
+  #define LIBUNWIND_AVAIL
+#endif
+
+/* error codes */
+enum {
+  UNW_ESUCCESS      = 0,     /* no error */
+  UNW_EUNSPEC       = -6540, /* unspecified (general) error */
+  UNW_ENOMEM        = -6541, /* out of memory */
+  UNW_EBADREG       = -6542, /* bad register number */
+  UNW_EREADONLYREG  = -6543, /* attempt to write read-only register */
+  UNW_ESTOPUNWIND   = -6544, /* stop unwinding */
+  UNW_EINVALIDIP    = -6545, /* invalid IP */
+  UNW_EBADFRAME     = -6546, /* bad frame */
+  UNW_EINVAL        = -6547, /* unsupported operation or bad value */
+  UNW_EBADVERSION   = -6548, /* unwind info has unsupported version */
+  UNW_ENOINFO       = -6549  /* no unwind info found */
+};
+
+struct unw_context_t {
+  uint64_t data[128];
+};
+typedef struct unw_context_t unw_context_t;
+
+struct unw_cursor_t {
+  uint64_t data[140];
+};
+typedef struct unw_cursor_t unw_cursor_t;
+
+typedef struct unw_addr_space *unw_addr_space_t;
+
+typedef int unw_regnum_t;
+typedef uint64_t unw_word_t;
+typedef double unw_fpreg_t;
+
+struct unw_proc_info_t {
+  unw_word_t  start_ip;         /* start address of function */
+  unw_word_t  end_ip;           /* address after end of function */
+  unw_word_t  lsda;             /* address of language specific data area, */
+                                /*  or zero if not used */
+  unw_word_t  handler;          /* personality routine, or zero if not used */
+  unw_word_t  gp;               /* not used */
+  unw_word_t  flags;            /* not used */
+  uint32_t    format;           /* compact unwind encoding, or zero if none */
+  uint32_t    unwind_info_size; /* size of dwarf unwind info, or zero if none */
+  unw_word_t  unwind_info;      /* address of dwarf unwind info, or zero */
+  unw_word_t  extra;            /* mach_header of mach-o image containing func */
+};
+typedef struct unw_proc_info_t unw_proc_info_t;
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+extern int unw_getcontext(unw_context_t *) LIBUNWIND_AVAIL;
+extern int unw_init_local(unw_cursor_t *, unw_context_t *) LIBUNWIND_AVAIL;
+extern int unw_step(unw_cursor_t *) LIBUNWIND_AVAIL;
+extern int unw_get_reg(unw_cursor_t *, unw_regnum_t, unw_word_t *) LIBUNWIND_AVAIL;
+extern int unw_get_fpreg(unw_cursor_t *, unw_regnum_t, unw_fpreg_t *) LIBUNWIND_AVAIL;
+extern int unw_set_reg(unw_cursor_t *, unw_regnum_t, unw_word_t) LIBUNWIND_AVAIL;
+extern int unw_set_fpreg(unw_cursor_t *, unw_regnum_t, unw_fpreg_t)  LIBUNWIND_AVAIL;
+extern int unw_resume(unw_cursor_t *) LIBUNWIND_AVAIL;
+
+extern const char *unw_regname(unw_cursor_t *, unw_regnum_t) LIBUNWIND_AVAIL;
+extern int unw_get_proc_info(unw_cursor_t *, unw_proc_info_t *) LIBUNWIND_AVAIL;
+extern int unw_is_fpreg(unw_cursor_t *, unw_regnum_t) LIBUNWIND_AVAIL;
+extern int unw_is_signal_frame(unw_cursor_t *) LIBUNWIND_AVAIL;
+extern int unw_get_proc_name(unw_cursor_t *, char *, size_t, unw_word_t *) LIBUNWIND_AVAIL;
+//extern int       unw_get_save_loc(unw_cursor_t*, int, unw_save_loc_t*);
+
+#if UNW_REMOTE
+/*
+ * Mac OS X "remote" API for unwinding other processes on same machine
+ *
+ */
+extern unw_addr_space_t unw_local_addr_space;
+extern unw_addr_space_t unw_create_addr_space_for_task(task_t);
+extern void unw_destroy_addr_space(unw_addr_space_t);
+extern int unw_init_remote_thread(unw_cursor_t *, unw_addr_space_t, thread_t *);
+#endif
+
+/*
+ * traditional libuwind "remote" API
+ *   NOT IMPLEMENTED on Mac OS X
+ *
+ * extern int               unw_init_remote(unw_cursor_t*, unw_addr_space_t,
+ *                                          thread_t*);
+ * extern unw_accessors_t   unw_get_accessors(unw_addr_space_t);
+ * extern unw_addr_space_t  unw_create_addr_space(unw_accessors_t, int);
+ * extern void              unw_flush_cache(unw_addr_space_t, unw_word_t,
+ *                                          unw_word_t);
+ * extern int               unw_set_caching_policy(unw_addr_space_t,
+ *                                                 unw_caching_policy_t);
+ * extern void              _U_dyn_register(unw_dyn_info_t*);
+ * extern void              _U_dyn_cancel(unw_dyn_info_t*);
+ */
+
+#ifdef __cplusplus
+}
+#endif
+
+// architecture independent register numbers
+enum {
+  UNW_REG_IP = -1, // instruction pointer
+  UNW_REG_SP = -2, // stack pointer
+};
+
+// 32-bit x86 registers
+enum {
+  UNW_X86_EAX = 0,
+  UNW_X86_ECX = 1,
+  UNW_X86_EDX = 2,
+  UNW_X86_EBX = 3,
+  UNW_X86_EBP = 4,
+  UNW_X86_ESP = 5,
+  UNW_X86_ESI = 6,
+  UNW_X86_EDI = 7
+};
+
+// 64-bit x86_64 registers
+enum {
+  UNW_X86_64_RAX = 0,
+  UNW_X86_64_RDX = 1,
+  UNW_X86_64_RCX = 2,
+  UNW_X86_64_RBX = 3,
+  UNW_X86_64_RSI = 4,
+  UNW_X86_64_RDI = 5,
+  UNW_X86_64_RBP = 6,
+  UNW_X86_64_RSP = 7,
+  UNW_X86_64_R8  = 8,
+  UNW_X86_64_R9  = 9,
+  UNW_X86_64_R10 = 10,
+  UNW_X86_64_R11 = 11,
+  UNW_X86_64_R12 = 12,
+  UNW_X86_64_R13 = 13,
+  UNW_X86_64_R14 = 14,
+  UNW_X86_64_R15 = 15
+};
+
+
+// 32-bit ppc register numbers
+enum {
+  UNW_PPC_R0  = 0,
+  UNW_PPC_R1  = 1,
+  UNW_PPC_R2  = 2,
+  UNW_PPC_R3  = 3,
+  UNW_PPC_R4  = 4,
+  UNW_PPC_R5  = 5,
+  UNW_PPC_R6  = 6,
+  UNW_PPC_R7  = 7,
+  UNW_PPC_R8  = 8,
+  UNW_PPC_R9  = 9,
+  UNW_PPC_R10 = 10,
+  UNW_PPC_R11 = 11,
+  UNW_PPC_R12 = 12,
+  UNW_PPC_R13 = 13,
+  UNW_PPC_R14 = 14,
+  UNW_PPC_R15 = 15,
+  UNW_PPC_R16 = 16,
+  UNW_PPC_R17 = 17,
+  UNW_PPC_R18 = 18,
+  UNW_PPC_R19 = 19,
+  UNW_PPC_R20 = 20,
+  UNW_PPC_R21 = 21,
+  UNW_PPC_R22 = 22,
+  UNW_PPC_R23 = 23,
+  UNW_PPC_R24 = 24,
+  UNW_PPC_R25 = 25,
+  UNW_PPC_R26 = 26,
+  UNW_PPC_R27 = 27,
+  UNW_PPC_R28 = 28,
+  UNW_PPC_R29 = 29,
+  UNW_PPC_R30 = 30,
+  UNW_PPC_R31 = 31,
+  UNW_PPC_F0  = 32,
+  UNW_PPC_F1  = 33,
+  UNW_PPC_F2  = 34,
+  UNW_PPC_F3  = 35,
+  UNW_PPC_F4  = 36,
+  UNW_PPC_F5  = 37,
+  UNW_PPC_F6  = 38,
+  UNW_PPC_F7  = 39,
+  UNW_PPC_F8  = 40,
+  UNW_PPC_F9  = 41,
+  UNW_PPC_F10 = 42,
+  UNW_PPC_F11 = 43,
+  UNW_PPC_F12 = 44,
+  UNW_PPC_F13 = 45,
+  UNW_PPC_F14 = 46,
+  UNW_PPC_F15 = 47,
+  UNW_PPC_F16 = 48,
+  UNW_PPC_F17 = 49,
+  UNW_PPC_F18 = 50,
+  UNW_PPC_F19 = 51,
+  UNW_PPC_F20 = 52,
+  UNW_PPC_F21 = 53,
+  UNW_PPC_F22 = 54,
+  UNW_PPC_F23 = 55,
+  UNW_PPC_F24 = 56,
+  UNW_PPC_F25 = 57,
+  UNW_PPC_F26 = 58,
+  UNW_PPC_F27 = 59,
+  UNW_PPC_F28 = 60,
+  UNW_PPC_F29 = 61,
+  UNW_PPC_F30 = 62,
+  UNW_PPC_F31 = 63,
+  UNW_PPC_MQ  = 64,
+  UNW_PPC_LR  = 65,
+  UNW_PPC_CTR = 66,
+  UNW_PPC_AP  = 67,
+  UNW_PPC_CR0 = 68,
+  UNW_PPC_CR1 = 69,
+  UNW_PPC_CR2 = 70,
+  UNW_PPC_CR3 = 71,
+  UNW_PPC_CR4 = 72,
+  UNW_PPC_CR5 = 73,
+  UNW_PPC_CR6 = 74,
+  UNW_PPC_CR7 = 75,
+  UNW_PPC_XER = 76,
+  UNW_PPC_V0  = 77,
+  UNW_PPC_V1  = 78,
+  UNW_PPC_V2  = 79,
+  UNW_PPC_V3  = 80,
+  UNW_PPC_V4  = 81,
+  UNW_PPC_V5  = 82,
+  UNW_PPC_V6  = 83,
+  UNW_PPC_V7  = 84,
+  UNW_PPC_V8  = 85,
+  UNW_PPC_V9  = 86,
+  UNW_PPC_V10 = 87,
+  UNW_PPC_V11 = 88,
+  UNW_PPC_V12 = 89,
+  UNW_PPC_V13 = 90,
+  UNW_PPC_V14 = 91,
+  UNW_PPC_V15 = 92,
+  UNW_PPC_V16 = 93,
+  UNW_PPC_V17 = 94,
+  UNW_PPC_V18 = 95,
+  UNW_PPC_V19 = 96,
+  UNW_PPC_V20 = 97,
+  UNW_PPC_V21 = 98,
+  UNW_PPC_V22 = 99,
+  UNW_PPC_V23 = 100,
+  UNW_PPC_V24 = 101,
+  UNW_PPC_V25 = 102,
+  UNW_PPC_V26 = 103,
+  UNW_PPC_V27 = 104,
+  UNW_PPC_V28 = 105,
+  UNW_PPC_V29 = 106,
+  UNW_PPC_V30 = 107,
+  UNW_PPC_V31 = 108,
+  UNW_PPC_VRSAVE  = 109,
+  UNW_PPC_VSCR    = 110,
+  UNW_PPC_SPE_ACC = 111,
+  UNW_PPC_SPEFSCR = 112
+};
+
+// 64-bit ARM64 registers
+enum {
+  UNW_ARM64_X0  = 0,
+  UNW_ARM64_X1  = 1,
+  UNW_ARM64_X2  = 2,
+  UNW_ARM64_X3  = 3,
+  UNW_ARM64_X4  = 4,
+  UNW_ARM64_X5  = 5,
+  UNW_ARM64_X6  = 6,
+  UNW_ARM64_X7  = 7,
+  UNW_ARM64_X8  = 8,
+  UNW_ARM64_X9  = 9,
+  UNW_ARM64_X10 = 10,
+  UNW_ARM64_X11 = 11,
+  UNW_ARM64_X12 = 12,
+  UNW_ARM64_X13 = 13,
+  UNW_ARM64_X14 = 14,
+  UNW_ARM64_X15 = 15,
+  UNW_ARM64_X16 = 16,
+  UNW_ARM64_X17 = 17,
+  UNW_ARM64_X18 = 18,
+  UNW_ARM64_X19 = 19,
+  UNW_ARM64_X20 = 20,
+  UNW_ARM64_X21 = 21,
+  UNW_ARM64_X22 = 22,
+  UNW_ARM64_X23 = 23,
+  UNW_ARM64_X24 = 24,
+  UNW_ARM64_X25 = 25,
+  UNW_ARM64_X26 = 26,
+  UNW_ARM64_X27 = 27,
+  UNW_ARM64_X28 = 28,
+  UNW_ARM64_X29 = 29,
+  UNW_ARM64_FP  = 29,
+  UNW_ARM64_X30 = 30,
+  UNW_ARM64_LR  = 30,
+  UNW_ARM64_X31 = 31,
+  UNW_ARM64_SP  = 31,
+  // reserved block
+  UNW_ARM64_D0  = 64,
+  UNW_ARM64_D1  = 65,
+  UNW_ARM64_D2  = 66,
+  UNW_ARM64_D3  = 67,
+  UNW_ARM64_D4  = 68,
+  UNW_ARM64_D5  = 69,
+  UNW_ARM64_D6  = 70,
+  UNW_ARM64_D7  = 71,
+  UNW_ARM64_D8  = 72,
+  UNW_ARM64_D9  = 73,
+  UNW_ARM64_D10 = 74,
+  UNW_ARM64_D11 = 75,
+  UNW_ARM64_D12 = 76,
+  UNW_ARM64_D13 = 77,
+  UNW_ARM64_D14 = 78,
+  UNW_ARM64_D15 = 79,
+  UNW_ARM64_D16 = 80,
+  UNW_ARM64_D17 = 81,
+  UNW_ARM64_D18 = 82,
+  UNW_ARM64_D19 = 83,
+  UNW_ARM64_D20 = 84,
+  UNW_ARM64_D21 = 85,
+  UNW_ARM64_D22 = 86,
+  UNW_ARM64_D23 = 87,
+  UNW_ARM64_D24 = 88,
+  UNW_ARM64_D25 = 89,
+  UNW_ARM64_D26 = 90,
+  UNW_ARM64_D27 = 91,
+  UNW_ARM64_D28 = 92,
+  UNW_ARM64_D29 = 93,
+  UNW_ARM64_D30 = 94,
+  UNW_ARM64_D31 = 95,
+};
+
+#endif