Implement support for breaking into debugger under Linux

include/internal/catch_debugger.h

@@ -25,25 +25,36 @@ namespace Catch{
     // http://cocoawithlove.com/2008/03/break-into-debugger.html
     #ifdef DEBUG
         #if defined(__ppc64__) || defined(__ppc__)
-            #define CATCH_BREAK_INTO_DEBUGGER() \
-                if( Catch::isDebuggerActive() ) { \
+            #define CATCH_TRAP() \
                     __asm__("li r0, 20\nsc\nnop\nli r0, 37\nli r4, 2\nsc\nnop\n" \
-                    : : : "memory","r0","r3","r4" ); \
-                }
+                    : : : "memory","r0","r3","r4" )
         #else
-            #define CATCH_BREAK_INTO_DEBUGGER() if( Catch::isDebuggerActive() ) {__asm__("int $3\n" : : );}
+            #define CATCH_TRAP() _asm__("int $3\n" : : )
         #endif
     #endif
 
+#elif defined(CATCH_PLATFORM_LINUX)
+    // If we can use inline assembler, do it because this allows us to break
+    // directly at the location of the failing check instead of breaking inside
+    // raise() called from it, i.e. one stack frame below.
+    #if defined(__GNUC__) && (defined(__i386) || defined(__x86_64))
+        #define CATCH_TRAP() asm volatile ("int $3")
+    #else // Fall back to the generic way.
+        #include <signal.h>
+
+        #define CATCH_TRAP() raise(SIGTRAP)
+    #endif
 #elif defined(_MSC_VER)
-    #define CATCH_BREAK_INTO_DEBUGGER() if( Catch::isDebuggerActive() ) { __debugbreak(); }
+    #define CATCH_TRAP() __debugbreak()
 #elif defined(__MINGW32__)
     extern "C" __declspec(dllimport) void __stdcall DebugBreak();
-    #define CATCH_BREAK_INTO_DEBUGGER() if( Catch::isDebuggerActive() ) { DebugBreak(); }
+    #define CATCH_TRAP() DebugBreak()
 #endif
 
-#ifndef CATCH_BREAK_INTO_DEBUGGER
-#define CATCH_BREAK_INTO_DEBUGGER() Catch::alwaysTrue();
+#ifdef CATCH_TRAP
+    #define CATCH_BREAK_INTO_DEBUGGER() if( Catch::isDebuggerActive() ) { CATCH_TRAP(); }
+#else
+    #define CATCH_BREAK_INTO_DEBUGGER() Catch::alwaysTrue();
 #endif
 
 #endif // TWOBLUECUBES_CATCH_DEBUGGER_H_INCLUDED

include/internal/catch_debugger.hpp

@@ -61,6 +61,33 @@
         }
     } // namespace Catch
 
+#elif defined(CATCH_PLATFORM_LINUX)
+    #include <fstream>
+    #include <string>
+
+    namespace Catch{
+        // The standard POSIX way of detecting a debugger is to attempt to
+        // ptrace() the process, but this needs to be done from a child and not
+        // this process itself to still allow attaching to this process later
+        // if wanted, so is rather heavy. Under Linux we have the PID of the
+        // "debugger" (which doesn't need to be gdb, of course, it could also
+        // be strace, for example) in /proc/$PID/status, so just get it from
+        // there instead.
+        bool isDebuggerActive(){
+            std::ifstream in("/proc/self/status");
+            for( std::string line; std::getline(in, line); ) {
+                static const int PREFIX_LEN = 11;
+                if( line.compare(0, PREFIX_LEN, "TracerPid:\t") == 0 ) {
+                    // We're traced if the PID is not 0 and no other PID starts
+                    // with 0 digit, so it's enough to check for just a single
+                    // character.
+                    return line.length() > PREFIX_LEN && line[PREFIX_LEN] != '0';
+                }
+            }
+
+            return false;
+        }
+    } // namespace Catch
 #elif defined(_MSC_VER)
     extern "C" __declspec(dllimport) int __stdcall IsDebuggerPresent();
     namespace Catch {

include/internal/catch_platform.h

@@ -15,6 +15,8 @@
 #define CATCH_PLATFORM_IPHONE
 #elif defined(WIN32) || defined(__WIN32__) || defined(_WIN32) || defined(_MSC_VER)
 #define CATCH_PLATFORM_WINDOWS
+#elif defined(linux) || defined(__linux) || defined(__linux__)
+#define CATCH_PLATFORM_LINUX
 #endif
 
 #endif // TWOBLUECUBES_CATCH_PLATFORM_H_INCLUDED