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[Bug debug/42896] New: [4.5 Regression] Random debug generation differences, bootstrap fails


Configuring with --enable-languages=c --disable-multilib --without-build-config
bootstrap fails with

Comparing stages 2 and 3
warning: gcc/cc1-checksum.o differs
warning: gcc/cc1obj-checksum.o differs
warning: gcc/cc1plus-checksum.o differs
Bootstrap comparison failure!
gcc/dse.o differs
make[2]: *** [compare] Error 1

The difference happens randomly but always at the same place.  The difference
is in .debug_loc only, readelf -w differences are:

--- /tmp/t1     2010-01-29 14:06:09.000000000 +0100
+++ /tmp/t2     2010-01-29 14:06:14.000000000 +0100
@@ -29471,7 +29471,7 @@
 Raw dump of debug contents of section .debug_line:

   Offset:                      0x0
-  Length:                      4841
+  Length:                      4837
   DWARF Version:               2
   Prologue Length:             691
   Minimum Instruction Length:  1
@@ -30960,7 +30960,7 @@
   Extended opcode 4: set Discriminator to 1
   Set is_stmt to 0
   Special opcode 159: advance Address by 11 to 0x2412 and Line by 0 to 1384
-  Extended opcode 4: set Discriminator to 6
+  Extended opcode 4: set Discriminator to 3
   Special opcode 61: advance Address by 4 to 0x2416 and Line by 0 to 1384
   Set is_stmt to 1
   Advance Line by 217 to 1601
@@ -31171,7 +31171,7 @@
   Special opcode 132: advance Address by 9 to 0x297b and Line by 1 to 1350
   Special opcode 76: advance Address by 5 to 0x2980 and Line by 1 to 1351
   Special opcode 109: advance Address by 7 to 0x2987 and Line by 6 to 1357
-  Extended opcode 4: set Discriminator to 6
+  Extended opcode 4: set Discriminator to 3
   Special opcode 174: advance Address by 12 to 0x2993 and Line by 1 to 1358
   Special opcode 160: advance Address by 11 to 0x299e and Line by 1 to 1359
   Special opcode 202: advance Address by 14 to 0x29ac and Line by 1 to 1360
@@ -31181,12 +31181,10 @@
   Set is_stmt to 0
   Advance PC by constant 17 to 0x29cc
   Special opcode 89: advance Address by 6 to 0x29d2 and Line by 0 to 1374
-  Extended opcode 4: set Discriminator to 3
-  Special opcode 145: advance Address by 10 to 0x29dc and Line by 0 to 1374
   Set is_stmt to 1
   Advance Line by 195 to 1569
-  Advance PC by constant 17 to 0x29ed
-  Special opcode 173: advance Address by 12 to 0x29f9 and Line by 0 to 1569
+  Advance PC by 39 to 0x29f9
+  Copy
   Special opcode 76: advance Address by 5 to 0x29fe and Line by 1 to 1570
   Extended opcode 4: set Discriminator to 1
   Set is_stmt to 0
@@ -31240,7 +31238,7 @@
   Special opcode 6: advance Address by 0 to 0x2b78 and Line by 1 to 1434
   Advance Line by -912 to 522
   Special opcode 145: advance Address by 10 to 0x2b82 and Line by 0 to 522
-  Extended opcode 4: set Discriminator to 3
+  Extended opcode 4: set Discriminator to 1
   Advance Line by 930 to 1452
   Advance PC by constant 17 to 0x2b93
   Special opcode 201: advance Address by 14 to 0x2ba1 and Line by 0 to 1452
@@ -34190,10 +34188,10 @@
     0000778d 00000000000048b1 00000000000048bb (DW_OP_reg2)
     0000778d 00000000000048bb 000000000000490b (DW_OP_reg5)
     0000778d 0000000000004bfb 0000000000004c00 (DW_OP_reg5)
-    0000778d 0000000000004c00 0000000000004c04 (DW_OP_breg7: 32)
+    0000778d 0000000000004c00 0000000000004c04 (DW_OP_breg3: 24)
     0000778d 0000000000004c1f 0000000000004c32 (DW_OP_reg5)
     0000778d 0000000000004e01 0000000000004e1b (DW_OP_reg5)
-    0000778d 0000000000004e1b 0000000000004e1f (DW_OP_breg7: 32)
+    0000778d 0000000000004e1b 0000000000004e1f (DW_OP_breg3: 24)
     0000778d <End of list>
     00007837 0000000000004921 00000000000049c1 (DW_OP_reg13)
     00007837 00000000000049c1 00000000000049cb (DW_OP_reg13)


I now run into this regularly because contrib/compare-debug does not work
for me as the host compiler inserts a .comment.SUSE.OPT section whose
content depends on whether -g is specified or not.


-- 
           Summary: [4.5 Regression] Random debug generation differences,
                    bootstrap fails
           Product: gcc
           Version: 4.5.0
            Status: UNCONFIRMED
          Keywords: build
          Severity: normal
          Priority: P3
         Component: debug
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: rguenth at gcc dot gnu dot org
GCC target triplet: x86_64-*-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42896


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