[llvm] [llvm][yaml2obj] Modify section header overriding timing (PR #130942)

[James Henderson via llvm-commits]

================
@@ -179,3 +179,34 @@ ProgramHeaders:
 # RUN:   FileCheck %s --check-prefix=INVALID-OFFSET
 
 # INVALID-OFFSET: yaml2obj: error: 'Offset' for segment with index 1 must be less than or equal to the minimum file offset of all included sections (0x78)
+
+## Document that the "Offset" value should be checked before the section offset is overriden using "ShOffset".
+## And the offset of the first section in a segment should not greater than the offset of the segment.
+# RUN: yaml2obj --docnum=4 %s -o %t5
+# RUN: llvm-readelf %t5 --sections --program-headers | FileCheck %s --check-prefix=SHOFFSET
+
+# SHOFFSET: [Nr] Name Type     Address          Off
+# SHOFFSET: [ 1] .foo PROGBITS 0000000000000000 0000ff
+
+# SHOFFSET:      Type Offset
+# SHOFFSET-NEXT: LOAD 0x000078
+
+--- !ELF
+FileHeader:
+  Class: ELFCLASS64
+  Data:  ELFDATA2LSB
+  Type:  ET_EXEC
+Sections:
+  - Name:     .foo
+    Type:     SHT_PROGBITS
+    Flags:    [ SHF_ALLOC ]
+    Size:     0x1
+## Note: the real .foo offset is much less than 0xFFFFFFFF or
+##       0xFFFFFF00, but no error is reported.
+    ShOffset: 0xFF
----------------
jh7370 wrote:

I'd make this substantially bigger. 0xFF might well be within the bounds of the file, whereas something like 0xFFFFFF wouldn't be. You could also be explicit about the real section offset, by adding an Offset field, to show the difference, but that's not a strict requirement of the test.

https://github.com/llvm/llvm-project/pull/130942