Debugging and stack traces on Mac OS X Lion

Mac OS X 10.7 Lion (really, Xcode 4) has changed the way that the system linker works in a way which makes debugging and interpreting stack traces difficult-to-impossible without special action.

From man ld,

Options when creating a main executable

-pie

This makes a special kind of main executable that is position independent (PIE).  On Mac OS X 10.5 and later, the OS the OS will load a PIE at a random address each time it is executed. You cannot create a PIE from .o files compiled with -mdynamic-no-pic. That means the codegen is less optimal, but the address randomization adds some security. When targeting Mac OS X 10.7 or later PIE is the default for main executables.

-no_pie

Do not make a position independent executable (PIE). This is the default, when targeting 10.6 and earlier.

With GNAT, as well as building with -g to keep debug symbols in the executable, you need to use the -E option to gnatbind to store an exception’s stack trace in the exception information. The result of Apple’s change is that you also need to link using -no_pie if you intend to use atos to interpret a stack trace, or gdb to debug your program. Without it,

failed in read/respond, Exception name: CONSTRAINT_ERROR
Message: ews-server-test.adb:133 explicit raise
Call stack traceback locations:
0x103712a31 0x103710110 0x103722d96 0x10370a98e 0x103709cb6 0x1037b50c6 0x7fff88fcc8bd

^C
$ atos -o ews-server-test 0x103712a31 0x103710110 0x103722d96 0x10370a98e 0x103709cb6 0x1037b50c6 0x7fff88fcc8bd
0x103712a31
0x103710110
0x103722d96
0x10370a98e
0x103709cb6
0x1037b50c6
0x7fff88fcc8bd

(in other words, nothing!) while with it,

$ gnatmake -P EWS -g -largs -Wl,-no_pie
$ ./ews-server-test
[...]
failed in read/respond, Exception name: CONSTRAINT_ERROR
Message: ews-server-test.adb:133 explicit raise
Call stack traceback locations:
0x10000aa31 0x100008110 0x10001ad96 0x10000298e 0x100001cb6 0x1000a30c6 0x7fff88fcc8bd

^C
$ atos -o ews-server-test 0x10000aa31 0x100008110 0x10001ad96 0x10000298e 0x100001cb6 0x1000a30c6 0x7fff88fcc8bd
ews__server__test__ajax_change.2355 (in ews-server-test) (ews-server-test.adb:133)
ews__dynamic__find (in ews-server-test) (ews-dynamic.adb:138)
ews__http__find (in ews-server-test) (ews-http.adb:472)
ews__server__respond (in ews-server-test) (ews-server.adb:206)
ews__server__serverTB (in ews-server-test) (ews-server.adb:124)
0x1000a30c6
0x7fff88fcc8bd

Edited 20.i.12 to mention the need for 'gnatbind -E’.
Edited 27.i.12 to mendion the need for 'gnatmake -g'.