[llvm-readelf] Fix emitting incorrect number of spaces in '--hex-dump'.

[Higuoxing]

Summary

This patch helps teach llvm-readelf to emit a correct number spaces when
dumping in hex format.

Before this patch, when the hex data doesn't fill the 4th column, some
spaces are missing.

Hex dump of section '.sec':
0x00000000 00000000 00000000 00000000 00000000 ................
0x00000010 00000000 00000000 00000000 0000 ..............

After this patch:

Hex dump of section '.sec':
0x00000000 00000000 00000000 00000000 00000000 ................
0x00000010 00000000 00000000 00000000 0000     ..............

[Higuoxing]

Fix test case label.

[grimar]

LGTM!

[jhenderson]

Some comment fixes. Please create a new commit for these and submit.

llvm/test/tools/llvm-readobj/ELF/hex-dump.test

52

Nits:
a correct -> the correct
amount -> number

55

This comment is clunky. Try:

"the column whose index isn't 4" -> "a column other than the last one"

64

Similarly:

"doesn't fill the last column"

73

fills the -> fills a

[Higuoxing]

In D84640#2178475, @jhenderson wrote:

Some comment fixes. Please create a new commit for these and submit.

Hi James, these comments are addressed in c12394fef3edc74207801adc6f778a0fb422f195.

---

Thank you both for reviewing!

llvm/test/tools/llvm-readobj/ELF/hex-dump.test

 ## Test that the -x alias can be used flexibly. Create a baseline and ensure
 ## all other combinations are identical.
-# RUN: yaml2obj %s -o %t
+# RUN: yaml2obj --docnum=1 %s -o %t
 # RUN: llvm-readelf --file-header --hex-dump=.shstrtab %t > %t.hexdump.out
 # RUN: llvm-readelf -h --hex-dump .shstrtab %t > %t.hexdump.1
 # RUN: llvm-readelf -h -x .shstrtab %t > %t.hexdump.2
 # RUN: llvm-readelf -h -x=.shstrtab %t > %t.hexdump.3
 # RUN: llvm-readelf -h -x.shstrtab %t > %t.hexdump.4
 # RUN: llvm-readelf -hx .shstrtab %t > %t.hexdump.5
 # RUN: llvm-readelf -hx=.shstrtab %t > %t.hexdump.6
 # RUN: llvm-readelf -hx.shstrtab %t > %t.hexdump.7

 # WARN: llvm-[[TOOL]]{{(\.exe)?}}: warning: '{{.*}}': could not find section 10
 
 --- !ELF
 FileHeader:
   Class:   ELFCLASS32
   Data:    ELFDATA2LSB
   Type:    ET_DYN
   Machine: EM_386
+
+## Test that llvm-readelf emits a correct amount of spaces between the hex data
+## and its ascii representation.
+
+## a) When the hex data doesn't fill the column whose index isn't 4.
+# RUN: yaml2obj --docnum=2 -DSIZE=18 %s -o %t2.out1
+# RUN: llvm-readelf --hex-dump=.sec %t2.out1 | \
+# RUN:   FileCheck %s --match-full-lines --strict-whitespace --check-prefix=SPACES1
+
+#      SPACES1:Hex dump of section '.sec':
+# SPACES1-NEXT:0x00000000 00000000 00000000 00000000 00000000 ................
+# SPACES1-NEXT:0x00000010 0000                                ..
+
+## b) When the hex data doesn't fill the column whose index is 4.
+# RUN: yaml2obj --docnum=2 -DSIZE=30 %s -o %t2.out2
+# RUN: llvm-readelf --hex-dump=.sec %t2.out2 | \
+# RUN:   FileCheck %s --match-full-lines --strict-whitespace --check-prefix=SPACES2
+
+#      SPACES2:Hex dump of section '.sec':
+# SPACES2-NEXT:0x00000000 00000000 00000000 00000000 00000000 ................
+# SPACES2-NEXT:0x00000010 00000000 00000000 00000000 0000     ..............
+
+## c) When the hex data fills the column.
+# RUN: yaml2obj --docnum=2 -DSIZE=28 %s -o %t2.out3
+# RUN: llvm-readelf --hex-dump=.sec %t2.out3 | \
+# RUN:   FileCheck %s --match-full-lines --strict-whitespace --check-prefix=SPACES3
+
+#      SPACES3:Hex dump of section '.sec':
+# SPACES3-NEXT:0x00000000 00000000 00000000 00000000 00000000 ................
+# SPACES3-NEXT:0x00000010 00000000 00000000 00000000          ............
+
+--- !ELF
+FileHeader:
+  Class:   ELFCLASS32
+  Data:    ELFDATA2LSB
+  Type:    ET_DYN
+  Machine: EM_386
+Sections:
+  - Name: .sec
+    Type: SHT_PROGBITS
+    Size: [[SIZE]]

llvm/tools/llvm-readobj/ObjDumper.cpp

for (const uint8_t *SecPtr = SecContent; SecPtr < SecEnd; SecPtr += 16) {
       }
 
       // We need to print the correct amount of spaces to match the format.
       // We are adding the (4 - i) last rows that are 8 characters each.
       // Then, the (4 - i) spaces that are in between the rows.
       // Least, if we cut in a middle of a row, we add the remaining characters,
       // which is (8 - (k * 2)).
       if (i < 4)
-        W.startLine() << format("%*c", (4 - i) * 8 + (4 - i) + (8 - (k * 2)),
-                                ' ');
+        W.startLine() << format("%*c", (4 - i) * 8 + (4 - i), ' ');
+      if (k < 4)
+        W.startLine() << format("%*c", 8 - k * 2, ' ');
 
       TmpSecPtr = SecPtr;
       for (i = 0; TmpSecPtr + i < SecEnd && i < 16; ++i)
         W.startLine() << (isPrint(TmpSecPtr[i])
                               ? static_cast<char>(TmpSecPtr[i])
                               : '.');
 
       W.startLine() << '\n';
     }
   }
 }
 
 } // namespace llvm