Messages in this thread Patches in this message | | | Date | Mon, 30 Jun 2003 09:20:15 +0400 | From | Samium Gromoff <> | Subject | [GCC] gcc vs. indentation |
| |
The story begun when i`ve started to make indentation fixes in the DAC960 driver. And in order to ensure i didn`t broke anything i was checking a diff between the resulting object files.
Surprisingly enough i`ve realised soon that indeed some indentation changes give gcc a reason to produce different code.
One of the cases is below, all three of them are in the attached .tar.gz file. The code in question is the 2.5.72-bk1 kernel, however there was no changes in the related code for some time, so plain .72 should be safe.
The examples are in the form of pairs of a C diff, and a "objdump -d" output diff.
The C diff: diff -X scripts/Xrule -urN 25/drivers/block/DAC960.c 25dac/drivers/block/DAC960.c --- 25/drivers/block/DAC960.c 2003-06-17 01:09:50.000000000 +0400 +++ 25dac/drivers/block/DAC960.c 2003-06-29 22:11:01.000000000 +0400 @@ -272,8 +272,7 @@ dma_addr_t RequestSenseDMA; struct pci_pool *RequestSensePool = NULL;
- if (Controller->FirmwareType == DAC960_V1_Controller) - { + if (Controller->FirmwareType == DAC960_V1_Controller) { CommandAllocationLength = offsetof(DAC960_Command_T, V1.EndMarker); CommandAllocationGroupSize = DAC960_V1_CommandAllocationGroupSize; ScatterGatherPool = pci_pool_create("DAC960_V1_ScatterGather", --- ./origDAC960.o.d 2003-06-29 21:02:55.000000000 +0400 +++ ./newDAC960.o.d 2003-06-29 22:13:46.000000000 +0400 @@ -1,5 +1,5 @@
-origDAC960.o: file format elf32-i386 +./newDAC960.o: file format elf32-i386
Disassembly of section .text:
@@ -5837,7 +5837,7 @@ 52a8: 84 c0 test %al,%al 52aa: 75 14 jne 52c0 <DAC960_V1_ProcessCompletedCommand+0x80> 52ac: 0f 0b ud2a - 52ae: 7d 0d jge 52bd <DAC960_V1_ProcessCompletedCommand+0x7d> + 52ae: 7c 0d jl 52bd <DAC960_V1_ProcessCompletedCommand+0x7d> 52b0: 27 daa 52b1: 00 00 add %al,(%eax) 52b3: 00 8d b6 00 00 00 add %cl,0xb6(%ebp) @@ -5951,7 +5951,7 @@ 5421: 84 c0 test %al,%al 5423: 0f 85 97 fe ff ff jne 52c0 <DAC960_V1_ProcessCompletedCommand+0x80> 5429: 0f 0b ud2a - 542b: 8f 0d 27 00 00 00 popl 0x27 + 542b: 8e 0d 27 00 00 00 movl 0x27,%cs 5431: e9 8a fe ff ff jmp 52c0 <DAC960_V1_ProcessCompletedCommand+0x80> 5436: 89 1c 24 mov %ebx,(%esp,1) 5439: e8 fc ff ff ff call 543a <DAC960_V1_ProcessCompletedCommand+0x1fa> @@ -7414,7 +7414,7 @@ 6ba2: 84 c0 test %al,%al 6ba4: 75 0a jne 6bb0 <DAC960_V2_ProcessCompletedCommand+0xa0> 6ba6: 0f 0b ud2a - 6ba8: bc 11 27 00 00 mov $0x2711,%esp + 6ba8: bb 11 27 00 00 mov $0x2711,%ebx 6bad: 00 89 f6 83 bc 24 add %cl,0x24bc83f6(%ecx) 6bb3: 84 00 test %al,(%eax) 6bb5: 00 00 add %al,(%eax)
Thats it. The point is i thought and hoped that gcc abstract syntax tree constructor is indentation invariant, and that is seemingly not true.
regards, Samium Gromoff [unhandled content-type:application/octet-stream] | |