[B2-devel] config problems

[Brian J. <bjj...@us...>]

I just tried getting the 0.9 snapshot to configure and build in SGI's
internal freeware build environment.  I ran into a few problems:

- the "extern "C" void exit(int) throw();" lines in the configure test
  programs were interfering with a "extern void exit(int);"
  declaration in SGI's unistd.h.  Deleting the " throw()"s fixed it.
  (Note:  when I run autoconf 2.13 directly, it doesn't have this
  problem.)

- the extended signal handlers test program was failing.  Eventually I
  tracked it down to SGI's C++ compiler:  it was optimizing out one of
  the writes to the page[] array, and moving the read of
  handler_called above the writes.  Here's a patch which fixed it.
  Just declaring the variables volatile doesn't seem to do it; I had
  to insert the system call to force synchronization:

--- sigsegv.cpp~        Sun May 20 22:21:54 2001
+++ sigsegv.cpp Mon Jun  4 14:20:44 2001
@@ -250,9 +250,9 @@
 #include <fcntl.h>
 #include <sys/mman.h>
 
-static caddr_t page = 0;
+static volatile caddr_t page = 0;
 static int page_size;
-static int handler_called = 0;
+static volatile int handler_called = 0;
 
 static bool sigsegv_test_handler(sigsegv_address_t fault_address, sigsegv_address_t instruction_address)
 {
@@ -281,6 +281,8 @@
        page[123] = 45;
        page[123] = 45;
 
+       (void)close(zero_fd);   // Be sure to read handler_called after writes!
+
        if (handler_called != 1)
                return 1;
 

There's probably a cleaner way to do this... but it works.  I probably
didn't see this problem before since I always ran configure with my
local machine's environment instead of the official SGI freeware build
environment, which may have changed the level of optimization used
while configuring.

						Brian

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   "There is the greatest practical benefit in making a few failures
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