Backtrace support for flang

flang/docs/Intrinsics.md

@@ -705,6 +705,7 @@ MALLOC, FREE
 
 ### Library subroutine 
 ```
+CALL BACKTRACE()
 CALL FDATE(TIME)
 CALL GETLOG(USRNAME)
 CALL GETENV(NAME [, VALUE, LENGTH, STATUS, TRIM_NAME, ERRMSG ])
@@ -769,7 +770,7 @@ This phase currently supports all the intrinsic procedures listed above but the
 | Intrinsic subroutines |MVBITS (elemental), CPU_TIME, DATE_AND_TIME, EVENT_QUERY, EXECUTE_COMMAND_LINE, GET_COMMAND, GET_COMMAND_ARGUMENT, GET_ENVIRONMENT_VARIABLE, MOVE_ALLOC, RANDOM_INIT, RANDOM_NUMBER, RANDOM_SEED, SIGNAL, SLEEP, SYSTEM, SYSTEM_CLOCK |
 | Atomic intrinsic subroutines | ATOMIC_ADD |
 | Collective intrinsic subroutines | CO_REDUCE |
-| Library subroutines | FDATE, GETLOG, GETENV |
+| Library subroutines | BACKTRACE, FDATE, GETLOG, GETENV |
 
 
 ### Intrinsic Function Folding

flang/include/flang/Runtime/stop.h

@@ -11,6 +11,7 @@
 
 #include "flang/Runtime/c-or-cpp.h"
 #include "flang/Runtime/entry-names.h"
+#include "flang/Runtime/extensions.h"
 #include <stdlib.h>
 
 FORTRAN_EXTERN_C_BEGIN
@@ -29,6 +30,7 @@ NORETURN void RTNAME(ProgramEndStatement)(NO_ARGUMENTS);
 // Extensions
 NORETURN void RTNAME(Exit)(int status DEFAULT_VALUE(EXIT_SUCCESS));
 NORETURN void RTNAME(Abort)(NO_ARGUMENTS);
+void FORTRAN_PROCEDURE_NAME(backtrace)(NO_ARGUMENTS);
 
 // Crash with an error message when the program dynamically violates a Fortran
 // constraint.

flang/runtime/CMakeLists.txt

@@ -59,6 +59,11 @@ if (CMAKE_SOURCE_DIR STREQUAL CMAKE_CURRENT_SOURCE_DIR)
     )
 endif()
 
+# function checks
+find_package(Backtrace)
+set(HAVE_BACKTRACE ${Backtrace_FOUND})
+set(BACKTRACE_HEADER ${Backtrace_HEADER})
+
 include(CheckCXXSymbolExists)
 include(CheckCXXSourceCompiles)
 check_cxx_symbol_exists(strerror_r string.h HAVE_STRERROR_R)

flang/runtime/config.h.cmake

@@ -8,4 +8,9 @@
    don't. */
 #cmakedefine01 HAVE_DECL_STRERROR_S
 
+/* Define to 1 if you have the `backtrace' function. */
+#cmakedefine HAVE_BACKTRACE ${HAVE_BACKTRACE}
+
+#define BACKTRACE_HEADER <${BACKTRACE_HEADER}>
+
 #endif

flang/runtime/stop.cpp

@@ -7,6 +7,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "flang/Runtime/stop.h"
+#include "config.h"
 #include "environment.h"
 #include "file.h"
 #include "io-error.h"
@@ -16,6 +17,10 @@
 #include <cstdio>
 #include <cstdlib>
 
+#ifdef HAVE_BACKTRACE
+#include BACKTRACE_HEADER
+#endif
+
 extern "C" {
 
 static void DescribeIEEESignaledExceptions() {
@@ -152,11 +157,36 @@ void RTNAME(PauseStatementText)(const char *code, std::size_t length) {
   std::exit(status);
 }
 
+static void PrintBacktrace() {
+#ifdef HAVE_BACKTRACE
+  // TODO: Need to parse DWARF information to print function line numbers
+  constexpr int MAX_CALL_STACK{999};
+  void *buffer[MAX_CALL_STACK];
+  int nptrs{backtrace(buffer, MAX_CALL_STACK)};
+
+  if (char **symbols{backtrace_symbols(buffer, nptrs)}) {
+    for (int i = 0; i < nptrs; i++) {
+      Fortran::runtime::Terminator{}.PrintCrashArgs("#%d %s\n", i, symbols[i]);
+    }
+    free(symbols);
+  }
+
+#else
+
+  // TODO: Need to implement the version for other platforms.
+  Fortran::runtime::Terminator{}.PrintCrashArgs(
+      "Handle the case when a backtrace is not available\n");
+
+#endif
+}
+
 [[noreturn]] void RTNAME(Abort)() {
-  // TODO: Add backtrace call, unless with `-fno-backtrace`.
+  PrintBacktrace();
   std::abort();
 }
 
+void FORTRAN_PROCEDURE_NAME(backtrace)() { PrintBacktrace(); }
+
 [[noreturn]] void RTNAME(ReportFatalUserError)(
     const char *message, const char *source, int line) {
   Fortran::runtime::Terminator{source, line}.Crash(message);