#11744: Latest Xcode update violates POSIX compliance of `nm -P` ---------------------------------+---------------------------------------- Reporter: hvr | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Build System | Version: Resolution: | Keywords: Operating System: MacOS X | Architecture: Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | ---------------------------------+---------------------------------------- Description changed by hvr: @@ -80,0 +80,13 @@ + + ---- + + Alternative workaround (since it turns out that Apple's `nm` violates + POSIX even more than assumed by not even supporting `nm -P -t x`): + + Have `deriveConstants` derive a known value, e.g. the value `0x1234` via + `char derivedConstantCONTROL_GROUP[1+0x1234];`, and if the value for + `CONTROL_GROUP` comes back as `18016` we know that we need to fixup all + decimal-wrongly-as-hex parsed integers, if it comes back as `4660` we + parsed correctly; any different value is a non-recoverable error + + This would also serve as a general integrity check for //all// platforms New description: TLDR: Apple messed up again and broke POSIX compliance luite ran into problems when he installed the latest Xcode update because the derived platform constants were off. He provided me the output of `nm -P ./includes/dist- derivedconstants/header/tmp.o` which turned out to have numbers which didn't make sense: {{{ _derivedConstantAP_STACK_SPLIM C 1025 0 _derivedConstantBITMAP_BITS_SHIFT C 7 0 _derivedConstantBLOCKS_PER_MBLOCK C 253 0 _derivedConstantBLOCK_SIZE C 4097 0 _derivedConstantCINT_SIZE C 5 0 _derivedConstantCLONG_LONG_SIZE C 9 0 _derivedConstantCLONG_SIZE C 9 0 _derivedConstantDOUBLE_SIZE C 9 0 _derivedConstantDYNAMIC_BY_DEFAULT C 2 0 ... }}} Which with an older Xcode version would have looked like {{{ _derivedConstantAP_STACK_SPLIM C 401 0 _derivedConstantBITMAP_BITS_SHIFT C 7 0 _derivedConstantBLOCKS_PER_MBLOCK C fd 0 _derivedConstantBLOCK_SIZE C 1001 0 _derivedConstantCINT_SIZE C 5 0 _derivedConstantCLONG_LONG_SIZE C 9 0 _derivedConstantCLONG_SIZE C 9 0 _derivedConstantDOUBLE_SIZE C 9 0 _derivedConstantDYNAMIC_BY_DEFAULT C 2 0 ... }}} So obviously `nm -P`'s output changed from hexadecimal to (non-compliant) decimal formatting of numbers. For reference, here's how POSIX specifies the semantics of `nm`: http://pubs.opengroup.org/onlinepubs/9699919799/utilities/nm.html ----
`-P` Write information in a portable output format, as specified in the STDOUT section.
...
If the `-P` option is specified, the previous information shall be displayed using the following portable format. The three versions differ depending on whether `-t d`, `-t o`, or `-t x` was specified, respectively:
{{{"%s%s %s %d %d\n",
, <name>, <type>, <value>, <size>}}} {{{"%s%s %s %o %o\n",
, <name>, <type>, <value>, <size>}}} {{{"%s%s %s %x %x\n",
, <name>, <type>, <value>, <size>}}}
...
'''If `-P` is specified, but `-t` is not, the format shall be as if `-t x` had been specified.'''
---- In the event that Apple can't be bothered to fix this bug (I've had bad experience with Apple and standard-compliance in the past, hence my pessimism) we could try to workaround by using `nm -P -t x` when building on OSX... ---- Alternative workaround (since it turns out that Apple's `nm` violates POSIX even more than assumed by not even supporting `nm -P -t x`): Have `deriveConstants` derive a known value, e.g. the value `0x1234` via `char derivedConstantCONTROL_GROUP[1+0x1234];`, and if the value for `CONTROL_GROUP` comes back as `18016` we know that we need to fixup all decimal-wrongly-as-hex parsed integers, if it comes back as `4660` we parsed correctly; any different value is a non-recoverable error This would also serve as a general integrity check for //all// platforms -- -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/11744#comment:4 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler