postgres.git / summary / log / commit / refs

commit    1b8f09dbd352cb2280ff6e7c8896db57a2d68f06
Author:   Andres Freund <andres@anarazel.de>
Date:     Thu Sep 13 21:18:43 2018 +0000
First released in: 12.0, 9.3.25, 9.4.20, 9.5.15, 9.6.11, 10.6, 11.0

    Error out for clang on x86-32 without SSE2 support, no -fexcess-precision.
    
    As clang currently doesn't support -fexcess-precision=standard,
    compiling x86-32 code with SSE2 disabled, can lead to problems with
    floating point overflow checks and the like.
    
    This issue was noticed because clang, on at least some BSDs, defaults
    to i386 compatibility, whereas it defaults to pentium4 on Linux.  Our
    forced usage of __builtin_isinf() lead to some overflow checks not
    triggering when compiling for i386, e.g. when the result of the
    calculation didn't overflow in 80bit registers, but did so in 64bit.
    
    While we could just fall back to a non-builtin isinf, it seems likely
    that the use of 80bit registers leads to other problems (which is why
    we force the flag for GCC already).  Therefore error out when
    detecting clang in that situation.
    
    Reported-By: Victor Wagner
    Analyzed-By: Andrew Gierth and Andres Freund
    Author: Andres Freund
    Discussion: https://postgr.es/m/20180905005130.ewk4xcs5dgyzcy45@alap3.anarazel.de
    Backpatch: 9.3-, all supported versions are affected


 configure    | 33 +++++++++++++++++++++++++++++++++
 configure.in | 18 ++++++++++++++++++
 2 files changed, 51 insertions(+)

diff --git a/configure b/configure
index 25fb1c7adb5..0c3bf1a5d87 100755
--- a/configure
+++ b/configure
@@ -5224,6 +5224,39 @@ fi
 rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
 fi
 
+# Defend against clang being used on x86-32 without SSE2 enabled.  As current
+# versions of clang do not understand -fexcess-precision=standard, the use of
+# x87 floating point operations leads to problems like isinf possibly returning
+# false for a value that is infinite when converted from the 80bit register to
+# the 8byte memory representation.
+#
+# Only perform the test if the compiler doesn't understand
+# -fexcess-precision=standard, that way a potentially fixed compiler will work
+# automatically.
+if test "$pgac_cv_prog_cc_cflags__fexcess_precision_standard" = no; then
+cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+int
+main ()
+{
+
+#if defined(__clang__) && defined(__i386__) && !defined(__SSE2_MATH__)
+choke me
+#endif
+
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_compile "$LINENO"; then :
+
+else
+  as_fn_error $? "Compiling PostgreSQL with clang, on 32bit x86, requires SSE2 support. Use -msse2 or use gcc." "$LINENO" 5
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+fi
+
 ac_ext=c
 ac_cpp='$CPP $CPPFLAGS'
 ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
diff --git a/configure.in b/configure.in
index 52748657553..119d8d882f1 100644
--- a/configure.in
+++ b/configure.in
@@ -551,6 +551,24 @@ choke me
 @%:@endif])], [], [AC_MSG_ERROR([do not put -ffast-math in CFLAGS])])
 fi
 
+# Defend against clang being used on x86-32 without SSE2 enabled.  As current
+# versions of clang do not understand -fexcess-precision=standard, the use of
+# x87 floating point operations leads to problems like isinf possibly returning
+# false for a value that is infinite when converted from the 80bit register to
+# the 8byte memory representation.
+#
+# Only perform the test if the compiler doesn't understand
+# -fexcess-precision=standard, that way a potentially fixed compiler will work
+# automatically.
+if test "$pgac_cv_prog_cc_cflags__fexcess_precision_standard" = no; then
+AC_COMPILE_IFELSE([AC_LANG_PROGRAM([], [
+@%:@if defined(__clang__) && defined(__i386__) && !defined(__SSE2_MATH__)
+choke me
+@%:@endif
+])], [],
+[AC_MSG_ERROR([Compiling PostgreSQL with clang, on 32bit x86, requires SSE2 support. Use -msse2 or use gcc.])])
+fi
+
 AC_PROG_CPP
 AC_SUBST(GCC)
 


[parent: ba20d392584c]