Determine at start time whether or not the underlying hardware supports

high-precision long double computations.

FossilOrigin-Name: 9a854b919667e0e679a259542b2ee444ee416dbd73ecd9458f6ced35d9d3f264

4 files changed, 39 insertions, 12 deletions

diff --git a/manifest b/manifest
index 1cb388428..05f0ad474 100644
--- a/manifest
+++ b/manifest
@@ -1,5 +1,5 @@
-C Doc\scorrections\sfor\sthe\sprevious\scheckin.
-D 2023-09-13T17:16:25.812
+C Determine\sat\sstart\stime\swhether\sor\snot\sthe\sunderlying\shardware\ssupports\nhigh-precision\slong\sdouble\scomputations.
+D 2023-09-13T20:06:46.382
 F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1
 F .fossil-settings/ignore-glob 35175cdfcf539b2318cb04a9901442804be81cd677d8b889fcc9149c21f239ea
 F LICENSE.md df5091916dbb40e6e9686186587125e1b2ff51f022cc334e886c19a0e9982724
@@ -672,7 +672,7 @@ F src/insert.c 3f0a94082d978bbdd33c38fefea15346c6c6bffb70bc645a71dc0f1f87dd3276
 F src/json.c 51141f1c09ccb177057e5813e6302a5e32e5ba88cc4a756318a35081010fc6df
 F src/legacy.c d7874bc885906868cd51e6c2156698f2754f02d9eee1bae2d687323c3ca8e5aa
 F src/loadext.c 98cfba10989b3da6f1807ad42444017742db7f100a54f1032af7a8b1295912c0
-F src/main.c 3a6f64cb47c605aa8b85de90474f448fc69366cd93ccf46a1276f5ec44c4a110
+F src/main.c d3489e9c6bb2953c341a1d21905e938cc637cf3eda3d45763c8783ad3e8a5df8
 F src/malloc.c 47b82c5daad557d9b963e3873e99c22570fb470719082c6658bf64e3012f7d23
 F src/mem0.c 6a55ebe57c46ca1a7d98da93aaa07f99f1059645
 F src/mem1.c 3bb59158c38e05f6270e761a9f435bf19827a264c13d1631c58b84bdc96d73b2
@@ -783,7 +783,7 @@ F src/vdbe.c 2849053c8625702b324a1553836b5abfcbc1559b4e49187e745dea349fb81685
 F src/vdbe.h 41485521f68e9437fdb7ec4a90f9d86ab294e9bb8281e33b235915e29122cfc0
 F src/vdbeInt.h 949669dfd8a41550d27dcb905b494f2ccde9a2e6c1b0b04daa1227e2e74c2b2c
 F src/vdbeapi.c 4184402246172220418c0ef49ff4cf1a19ced9a4ac6c843c2f0773fb5c543f37
-F src/vdbeaux.c e3aa5c46827cd95e0fc4d0f302fa3e901ab5f07258fdbb42709eeef40f63018d
+F src/vdbeaux.c 1b58fc93843b04d3e96d3240e554ed9f23b2e308d3b736f1004fe2eb514a8893
 F src/vdbeblob.c 2516697b3ee8154eb8915f29466fb5d4f1ae39ee8b755ea909cefaf57ec5e2ce
 F src/vdbemem.c 317b9f48708139db6239ade40c7980b4bc8233168383690d588dad6d8437f722
 F src/vdbesort.c 0d40dca073c94e158ead752ef4225f4fee22dee84145e8c00ca2309afb489015
@@ -2120,8 +2120,11 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
 F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
 F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P fa1c1534724b03debc83ae35c2fadab83faf4b4e62b91981fed103888de41396
-R fc8b92583c5ee29edc69eeeb7f6870d1
-U stephan
-Z 791cbb18afe40734ee4314c018ff0246
+P 9ea0a9f39d03707d251af5af08d1ba94958704ba74019d7e8823ccd21936023c
+R 9d032fc0954884df48b056f822f415bb
+T *branch * runtime-longdouble-test
+T *sym-runtime-longdouble-test *
+T -sym-trunk *
+U drh
+Z 4050589208bc39d1cdb1d56c5679577d
 # Remove this line to create a well-formed Fossil manifest.
diff --git a/manifest.uuid b/manifest.uuid
index 31cd73859..8466fcf0c 100644
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-9ea0a9f39d03707d251af5af08d1ba94958704ba74019d7e8823ccd21936023c
\ No newline at end of file
+9a854b919667e0e679a259542b2ee444ee416dbd73ecd9458f6ced35d9d3f264
\ No newline at end of file
diff --git a/src/main.c b/src/main.c
index d69ebf75b..59f90197f 100644
--- a/src/main.c
+++ b/src/main.c
@@ -160,6 +160,26 @@ char *sqlite3_temp_directory = 0;
 char *sqlite3_data_directory = 0;
 
 /*
+** Determine what the default bUseLongDouble value should be and set it.
+*/
+static SQLITE_NOINLINE int hasHighPrecisionDouble(int rc){
+  if( sizeof(LONGDOUBLE_TYPE)<=8 ){
+    return 0;
+  }else{
+    /* Just because sizeof(long double)>8 does not mean that the underlying
+    ** hardware actually supports high-precision floating point.  Do a test
+    ** to verify that it really does */
+    LONGDOUBLE_TYPE a, b, c;
+    rc++;
+    a = 1.0+rc*0.1;
+    b = 1.0e+18+rc*25.0;
+    c = a+b;
+    return b!=c;
+  }
+}
+
+
+/*
 ** Initialize SQLite. 
 **
 ** This routine must be called to initialize the memory allocation,
@@ -354,6 +374,10 @@ int sqlite3_initialize(void){
   }
 #endif
 
+  /* Experimentally determine if high-precision floating point is
+  ** available. */
+  sqlite3Config.bUseLongDouble = hasHighPrecisionDouble(rc);
+
   return rc;
 }
 
@@ -4554,11 +4578,11 @@ int sqlite3_test_control(int op, ...){
     **   X<0     Make no changes to the bUseLongDouble.  Just report value.
     **   X==0    Disable bUseLongDouble
     **   X==1    Enable bUseLongDouble
-    **   X==2    Set bUseLongDouble to its default value for this platform
+    **   X>=2    Set bUseLongDouble to its default value for this platform
     */
     case SQLITE_TESTCTRL_USELONGDOUBLE: {
       int b = va_arg(ap, int);
-      if( b==2 ) b = sizeof(LONGDOUBLE_TYPE)>8;
+      if( b>=2 ) b = hasHighPrecisionDouble(b);
       if( b>=0 ) sqlite3Config.bUseLongDouble = b>0;
       rc = sqlite3Config.bUseLongDouble!=0;
       break;
diff --git a/src/vdbeaux.c b/src/vdbeaux.c
index 225c8d12c..106b8073c 100644
--- a/src/vdbeaux.c
+++ b/src/vdbeaux.c
@@ -4467,7 +4467,7 @@ SQLITE_NOINLINE int sqlite3BlobCompare(const Mem *pB1, const Mem *pB2){
 ** equal to, or greater than the second (double).
 */
 int sqlite3IntFloatCompare(i64 i, double r){
-  if( sizeof(LONGDOUBLE_TYPE)>8 ){
+  if( sqlite3Config.bUseLongDouble ){
     LONGDOUBLE_TYPE x = (LONGDOUBLE_TYPE)i;
     testcase( x<r );
     testcase( x>r );