diff options
Diffstat (limited to 'aclocal.m4')
| -rw-r--r-- | aclocal.m4 | 38 |
1 files changed, 33 insertions, 5 deletions
diff --git a/aclocal.m4 b/aclocal.m4 index 5b037326be..d2d42f243b 100644 --- a/aclocal.m4 +++ b/aclocal.m4 @@ -288,11 +288,31 @@ AC_DEFUN([FPTOOLS_SET_HASKELL_PLATFORM_VARS], esac } + dnl Note [autoconf assembler checks and -flto] + dnl ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + dnl + dnl Autoconf's AC_COMPILE_IFELSE macro is fragile in the case of checks + dnl which require that the assembler is run. Specifically, GCC does not run + dnl the assembler if invoked with `-c -flto`; it merely dumps its internal + dnl AST to the object file, to be compiled and assembled during the final + dnl link. + dnl + dnl This can cause configure checks like that for the + dnl .subsections_via_symbols directive to pass unexpected (see #16440), + dnl leading the build system to incorrectly conclude that the directive is + dnl supported. + dnl + dnl For this reason, it is important that configure checks that rely on the + dnl assembler failing use AC_LINK_IFELSE rather than AC_COMPILE_IFELSE, + dnl ensuring that the assembler sees the check. + dnl + dnl ** check for Apple-style dead-stripping support dnl (.subsections-via-symbols assembler directive) AC_MSG_CHECKING(for .subsections_via_symbols) - AC_COMPILE_IFELSE( + dnl See Note [autoconf assembler checks and -flto] + AC_LINK_IFELSE( [AC_LANG_PROGRAM([], [__asm__ (".subsections_via_symbols");])], [AC_MSG_RESULT(yes) HaskellHaveSubsectionsViaSymbols=True @@ -305,8 +325,9 @@ AC_DEFUN([FPTOOLS_SET_HASKELL_PLATFORM_VARS], dnl ** check for .ident assembler directive AC_MSG_CHECKING(whether your assembler supports .ident directive) - AC_COMPILE_IFELSE( - [AC_LANG_SOURCE([__asm__ (".ident \"GHC x.y.z\"");])], + dnl See Note [autoconf assembler checks and -flto] + AC_LINK_IFELSE( + [AC_LANG_PROGRAM([__asm__ (".ident \"GHC x.y.z\"");], [])], [AC_MSG_RESULT(yes) HaskellHaveIdentDirective=True], [AC_MSG_RESULT(no) @@ -330,8 +351,15 @@ AC_DEFUN([FPTOOLS_SET_HASKELL_PLATFORM_VARS], ;; esac AC_MSG_CHECKING(for GNU non-executable stack support) - AC_COMPILE_IFELSE( - [AC_LANG_PROGRAM([__asm__ (".section .note.GNU-stack,\"\",$progbits");], [0])], + dnl See Note [autoconf assembler checks and -flto] + AC_LINK_IFELSE( + dnl the `main` function is placed after the .note.GNU-stack directive + dnl so we need to ensure that the active segment is correctly set, + dnl otherwise `main` will be placed in the wrong segment. + [AC_LANG_PROGRAM([ + __asm__ (".section .note.GNU-stack,\"\",$progbits"); + __asm__ (".section .text"); + ], [0])], [AC_MSG_RESULT(yes) HaskellHaveGnuNonexecStack=True], [AC_MSG_RESULT(no) |