Subject: [PATCH] Limit the "precision" of floating-point to text conversions
 in the printf() function to 100,000,000.

---
 src/printf.c     | 12 ++++++++++++
 test/printf.test | 16 +++++++++++++---
 2 files changed, 25 insertions(+), 3 deletions(-)

diff --git a/src/printf.c b/src/printf.c
index 7bce83f..260bf79 100644
--- a/src/printf.c
+++ b/src/printf.c
@@ -165,6 +165,13 @@ static char *getTextArg(PrintfArguments *p){
 #endif
 #define etBUFSIZE SQLITE_PRINT_BUF_SIZE  /* Size of the output buffer */
 
+/*
+** Hard limit on the precision of floating-point conversions.
+*/
+#ifndef SQLITE_PRINTF_PRECISION_LIMIT
+# define SQLITE_FP_PRECISION_LIMIT 100000000
+#endif
+
 /*
 ** Render a string given by "fmt" into the StrAccum object.
 */
@@ -471,6 +478,11 @@ void sqlite3_str_vappendf(
         length = 0;
 #else
         if( precision<0 ) precision = 6;         /* Set default precision */
+#ifdef SQLITE_FP_PRECISION_LIMIT
+        if( precision>SQLITE_FP_PRECISION_LIMIT ){
+          precision = SQLITE_FP_PRECISION_LIMIT;
+        }
+#endif
         if( realvalue<0.0 ){
           realvalue = -realvalue;
           prefix = '-';
diff --git a/test/printf.test b/test/printf.test
index d768898..a2b5e2a 100644
--- a/test/printf.test
+++ b/test/printf.test
@@ -538,9 +538,11 @@ do_test printf-2.1.2.8 {
 do_test printf-2.1.2.9 {
   sqlite3_mprintf_double {abc: %d %d (%1.1g) :xyz} 1 1 1.0e-20
 } {abc: 1 1 (1e-20) :xyz}
-do_test printf-2.1.2.10 {
-  sqlite3_mprintf_double {abc: %*.*f}  2000000000 1000000000 1.0e-20
-} {abc: }
+if {$SQLITE_MAX_LENGTH<=[expr 1000*1000*1000]} {
+  do_test printf-2.1.2.10 {
+    sqlite3_mprintf_double {abc: %*.*f}  2000000000 1000000000 1.0e-20
+  } {}
+}
 do_test printf-2.1.3.1 {
   sqlite3_mprintf_double {abc: (%*.*f) :xyz} 1 1 1.0
 } {abc: (1.0) :xyz}
@@ -3777,4 +3779,12 @@ foreach ::iRepeat {0 1} {
   }
 }
 
+# 2020-05-23
+# ticket 23439ea582241138
+#
+do_execsql_test printf-16.1 {
+  SELECT printf('%.*g',2147483647,0.01);
+} {0.01}
+
+
 finish_test
-- 
2.24.1