| 1 | dnl @synopsis AX_CHECK_SYSCALL_LSEEK([ACTION-IF-TRUE], [ACTION-IF-FALSE]) |
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| 2 | dnl |
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| 3 | dnl This macro will find out if the lseek syscall requires a dummy middle |
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| 4 | dnl parameter |
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| 5 | dnl |
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| 6 | dnl The following defines will be set as appropriate: |
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| 7 | dnl HAVE_LSEEK_DUMMY_PARAM |
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| 8 | dnl Also ACTION-IF-TRUE and ACTION-IF-FALSE are run as appropriate |
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| 9 | dnl |
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| 10 | dnl @category C |
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| 11 | dnl @author Martin Ebourne |
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| 12 | dnl @version 2005/07/03 |
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| 13 | dnl @license AllPermissive |
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| 14 | |
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| 15 | AC_DEFUN([AX_CHECK_SYSCALL_LSEEK], [ |
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| 16 | AC_REQUIRE([AX_FUNC_SYSCALL])dnl |
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| 17 | if test "x$ac_cv_header_sys_syscall_h" = "xyes"; then |
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| 18 | AC_CACHE_CHECK([[whether syscall lseek requires dummy parameter]], [box_cv_have_lseek_dummy_param], |
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| 19 | [AC_TRY_RUN( |
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| 20 | [ |
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| 21 | $ac_includes_default |
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| 22 | #include <fcntl.h> |
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| 23 | #include <sys/syscall.h> |
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| 24 | #ifdef HAVE___SYSCALL_NEED_DEFN |
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| 25 | extern "C" off_t __syscall(quad_t number, ...); |
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| 26 | #endif |
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| 27 | #ifdef HAVE___SYSCALL // always use it if we have it |
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| 28 | #undef syscall |
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| 29 | #define syscall __syscall |
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| 30 | #endif |
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| 31 | int main() |
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| 32 | { |
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| 33 | int fh = creat("lseektest", 0600); |
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| 34 | int res = 0; |
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| 35 | if(fh>=0) |
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| 36 | { |
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| 37 | // This test tries first to seek to position 0, with NO |
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| 38 | // "dummy argument". If lseek does actually require a dummy |
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| 39 | // argument, then it will eat SEEK_SET for the offset and |
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| 40 | // try to use 99 as whence, which is invalid, so res will be |
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| 41 | // -1, the program will return zero and |
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| 42 | // have_lseek_dummy_param=yes |
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| 43 | // (whew! that took 1 hour to figure out) |
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| 44 | // The "dummy argument" probably means that it takes a 64-bit |
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| 45 | // offset, so this was probably a bug anyway, and now that |
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| 46 | // we cast the offset to off_t, it should never be needed |
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| 47 | // (if my reasoning is correct). |
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| 48 | res = syscall(SYS_lseek, fh, (off_t)0, SEEK_SET, 99); |
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| 49 | close(fh); |
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| 50 | } |
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| 51 | unlink("lseektest"); |
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| 52 | return res!=-1; |
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| 53 | } |
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| 54 | ], |
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| 55 | [box_cv_have_lseek_dummy_param=yes], |
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| 56 | [box_cv_have_lseek_dummy_param=no], |
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| 57 | [box_cv_have_lseek_dummy_param=no # assume not for cross-compiling] |
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| 58 | )]) |
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| 59 | if test "x$box_cv_have_lseek_dummy_param" = "xyes"; then |
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| 60 | AC_DEFINE([HAVE_LSEEK_DUMMY_PARAM], 1, |
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| 61 | [Define to 1 if syscall lseek requires a dummy middle parameter]) |
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| 62 | fi |
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| 63 | fi |
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| 64 | if test "x$box_cv_have_lseek_dummy_param" = "xno" |
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| 65 | then |
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| 66 | m4_ifvaln([$1],[$1],[:])dnl |
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| 67 | m4_ifvaln([$2],[else $2])dnl |
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| 68 | fi |
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| 69 | ])dnl |
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