Improved comments on the work-around to the GCC x86 floating point wonkiness.

FossilOrigin-Name: 7b4c16731e7bf6f03f5adf4fcb2008c0b19be473fb1b90b405c217c08916586a

diff --git a/manifest b/manifest
index f132d2fafa044789e83b7519ccebfcfe03c0ef33..079596dfbecd07a169fc01b648d8c450839453d6 100644 (file)
--- a/manifest
+++ b/manifest
@@ -1,5 +1,5 @@
-C Work\saround\sfor\san\sapparent\sGCC\sbug.\s\sSee\n[forum:/info/ee7278611394034c|forum\spost\see7278611394034c]\sfor\sdetails.
-D 2023-07-05T18:59:52.671
+C Improved\scomments\son\sthe\swork-around\sto\sthe\sGCC\sx86\sfloating\spoint\swonkiness.
+D 2023-07-05T19:56:14.847
 F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1
 F .fossil-settings/ignore-glob 35175cdfcf539b2318cb04a9901442804be81cd677d8b889fcc9149c21f239ea
 F LICENSE.md df5091916dbb40e6e9686186587125e1b2ff51f022cc334e886c19a0e9982724
@@ -705,7 +705,7 @@ F src/trigger.c ad6ab9452715fa9a8075442e15196022275b414b9141b566af8cdb7a1605f2b0
 F src/update.c 0aa36561167a7c40d01163238c297297962f31a15a8d742216b3c37cdf25f731
 F src/upsert.c 5303dc6c518fa7d4b280ec65170f465c7a70b7ac2b22491598f6d0b4875b3145
 F src/utf.c ee39565f0843775cc2c81135751ddd93eceb91a673ea2c57f61c76f288b041a0
-F src/util.c c8a4c99081e378a4562e24f6c2e81319dc2d399c82c12f9b75ad3fd5ecde178d
+F src/util.c 49a7335c225a7019d4b81606d65d105856a181ed122f25338d2323174a6e4a93
 F src/vacuum.c 604fcdaebe76f3497c855afcbf91b8fa5046b32de3045bab89cc008d68e40104
 F src/vdbe.c 74282a947234513872a83b0bab1b8c644ece64b3e27b053ef17677c8ff9c81e0
 F src/vdbe.h 41485521f68e9437fdb7ec4a90f9d86ab294e9bb8281e33b235915e29122cfc0
@@ -2043,8 +2043,8 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
 F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
 F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P 28f57b34e6b11184a36e363a985e7531bddd7be48a5e039a670e5acf748eedda
-R c8ff71fb703fd93e733ec7777485c76e
+P 5d9e9364808793d65925d4efbfde0f4246df258758f15e8ce1105070d1018fe6
+R 721b48a97d77f38539bb9af05ab5869d
 U drh
-Z ae8486dcf7227b47ea3089bba703cbf5
+Z c80d89ca100028001e859be8d9af6fed
 # Remove this line to create a well-formed Fossil manifest.

diff --git a/manifest.uuid b/manifest.uuid
index 35588ce08dda71a38dc4f5a0425743f4c34c9e27..e14a61843666ce2d3269773388f7e5acba625f37 100644 (file)
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-5d9e9364808793d65925d4efbfde0f4246df258758f15e8ce1105070d1018fe6
\ No newline at end of file
+7b4c16731e7bf6f03f5adf4fcb2008c0b19be473fb1b90b405c217c08916586a
\ No newline at end of file

diff --git a/src/util.c b/src/util.c
index 52dc09a7d2ea7c3b82e5b7a5950dfaae287a93b8..6b757e4fb71c9d4e0c12188b4f992a0d55dedaaa 100644 (file)
--- a/src/util.c
+++ b/src/util.c
@@ -387,9 +387,20 @@ u8 sqlite3StrIHash(const char *z){
 }
 
 /*
-** Work around an apparent bug in GCC.
+** Work around an issue in GCC where it generates code that stores
+** intermediate results to a higher precision than binary64.  This
+** messes up the Dekker algorithm.  See the discussion at
 ** https://sqlite.org/forum/info/ee7278611394034c
+**
+** By adding the -ffloat-store option, it forces GCC to truncate
+** intermediate results to the correct precision.  The GCC devs
+** recommended -fexcess-precision=standard or -std=c99.  Those options
+** work too, from the command-line, but I could not get them to work
+** as a #pragma.  We want the "sqlite3.c" to "just work" without
+** requiring any special compiler-options, so we continue to use
+** the -ffloat-store method of working around the issue.
 */
+
 #ifdef i386
 #pragma GCC push_options
 #pragma GCC optimize("float-store")
@@ -423,7 +434,7 @@ static void dekkerMul2(double *x, double y, double yy){
   x[1] += cc;
 }
 
-/* End of the GCC bug work-around */
+/* End of the GCC x86 floating-point work-around */
 #ifdef i386
 #pragma GCC pop_options
 #endif