fix printing of %llx very small and very large values

2 files changed, 23 insertions, 1 deletions

diff --git a/src/library.js b/src/library.js
index 51921541..79f1c285 100644
--- a/src/library.js
+++ b/src/library.js
@@ -2822,7 +2822,14 @@ LibraryManager.library = {
             prefix = flagAlternative ? '0x' : '';
 #if PRECISE_I64_MATH
             if (argSize == 8 && i64Math) {
-              argText = (origArg[1] ? (origArg[1]>>>0).toString(16) : '') + (origArg[0]>>>0).toString(16);
+              if (origArg[1]) {
+                argText = (origArg[1]>>>0).toString(16);
+                var lower = (origArg[0]>>>0).toString(16);
+                while (lower.length < 8) lower = '0' + lower;
+                argText += lower;
+              } else {
+                argText = (origArg[0]>>>0).toString(16);
+              }
             } else
 #endif
             if (currArg < 0) {
diff --git a/tests/runner.py b/tests/runner.py
index a5eb7ede..b93300d5 100755
--- a/tests/runner.py
+++ b/tests/runner.py
@@ -5254,6 +5254,8 @@ at function.:blag
       self.do_run(src, re.sub('(^|\n)\s+', '\\1', expected))
 
     def test_vsnprintf(self):
+      if self.emcc_args is None: return self.skip('needs i64 math')
+
       src = r'''
         #include <stdio.h>
         #include <stdarg.h>
@@ -5279,6 +5281,17 @@ at function.:blag
           printy("0x%llx_0x%llx", y, x);
           printy("0x%llx_0x%llx", y, y);
 
+          {
+            uint64_t A = 0x800000;
+            uint64_t B = 0x800000000000ULL;
+            printy("0x%llx_0x%llx", A, B);
+          }
+          {
+            uint64_t A = 0x800;
+            uint64_t B = 0x12340000000000ULL;
+            printy("0x%llx_0x%llx", A, B);
+          }
+
           return 0;
         }
       '''
@@ -5286,6 +5299,8 @@ at function.:blag
 0x0_0x0
 0x400000_0x0
 0x400000_0x400000
+0x800000_0x800000000000
+0x800_0x12340000000000
 ''')
 
     def test_printf_more(self):