MC: Support larger COFF string tables

Single-slash encoded entries do not require a terminating null. This bumps
the maximum table size from ~1MB to ~9.5MB.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@187352 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/MC/WinCOFFObjectWriter.cpp b/lib/MC/WinCOFFObjectWriter.cpp
index 28e611f6d73383ba0ee766868d6962c7230dec33..4e269348036a4cc0b45443c097caf39a407d6702 100644 (file)
--- a/lib/MC/WinCOFFObjectWriter.cpp
+++ b/lib/MC/WinCOFFObjectWriter.cpp
@@ -475,18 +475,21 @@ void WinCOFFObjectWriter::DefineSymbol(MCSymbolData const &SymbolData,
 /// name into the string table if needed
 void WinCOFFObjectWriter::MakeSectionReal(COFFSection &S, size_t Number) {
   if (S.Name.size() > COFF::NameSize) {
-    size_t StringTableEntry = Strings.insert(S.Name.c_str());
-
-    // FIXME: Why is this number 999999? This number is never mentioned in the
-    // spec. I'm assuming this is due to the printed value needing to fit into
-    // the S.Header.Name field. In which case why not 9999999 (7 9's instead of
-    // 6)? The spec does not state if this entry should be null terminated in
-    // this case, and thus this seems to be the best way to do it. I think I
-    // just solved my own FIXME...
-    if (StringTableEntry > 999999)
-      report_fatal_error("COFF string table is greater than 999999 bytes.");
-
-    std::sprintf(S.Header.Name, "/%d", unsigned(StringTableEntry));
+    const unsigned Max6DecimalSize = 999999;
+    const unsigned Max7DecimalSize = 9999999;
+    uint64_t StringTableEntry = Strings.insert(S.Name.c_str());
+
+    if (StringTableEntry <= Max6DecimalSize) {
+      std::sprintf(S.Header.Name, "/%d", unsigned(StringTableEntry));
+    } else if (StringTableEntry <= Max7DecimalSize) {
+      // With seven digits, we have to skip the terminating null. Because
+      // sprintf always appends it, we use a larger temporary buffer.
+      char buffer[9] = { };
+      std::sprintf(buffer, "/%d", unsigned(StringTableEntry));
+      std::memcpy(S.Header.Name, buffer, 8);
+    } else {
+      report_fatal_error("COFF string table is greater than 9,999,999 bytes.");
+    }
   } else
     std::memcpy(S.Header.Name, S.Name.c_str(), S.Name.size());
 

diff --git a/test/MC/COFF/section-name-encoding.s b/test/MC/COFF/section-name-encoding.s
new file mode 100644 (file)
index 0000000..0f531f3
--- /dev/null
+++ b/test/MC/COFF/section-name-encoding.s
@@ -0,0 +1,62 @@
+// Check that COFF section names are properly encoded.
+//
+// Encodings for different lengths:
+//   [0, 8]:               raw name
+//   (8, 999999]:          base 10 string table index (/9999999)
+//
+// RUN: llvm-mc -triple x86_64-pc-win32 -filetype=obj %s | llvm-readobj -s | FileCheck %s
+
+// Raw encoding
+
+// CHECK:   Section {
+// CHECK:     Number: 1
+// CHECK:     Name: s (73 00 00 00 00 00 00 00)
+// CHECK:   }
+// CHECK:   Section {
+// CHECK:     Number: 2
+// CHECK:     Name: s1234567 (73 31 32 33 34 35 36 37)
+// CHECK:   }
+.section s;        .long 1
+.section s1234567; .long 1
+
+
+// Base 10 encoding
+
+// /4
+// CHECK:   Section {
+// CHECK:     Number: 3
+// CHECK:     Name: s12345678 (2F 34 00 00 00 00 00 00)
+// CHECK:   }
+.section s12345678; .long 1
+
+
+// Generate padding sections to increase the string table size to at least
+// 1,000,000 bytes.
+.macro pad_sections2 pad
+  // 10x \pad
+  .section p0\pad\pad\pad\pad\pad\pad\pad\pad\pad\pad; .long 1
+  .section p1\pad\pad\pad\pad\pad\pad\pad\pad\pad\pad; .long 1
+  .section p2\pad\pad\pad\pad\pad\pad\pad\pad\pad\pad; .long 1
+  .section p3\pad\pad\pad\pad\pad\pad\pad\pad\pad\pad; .long 1
+  .section p4\pad\pad\pad\pad\pad\pad\pad\pad\pad\pad; .long 1
+.endm
+
+.macro pad_sections pad
+  // 20x \pad
+  pad_sections2 \pad\pad\pad\pad\pad\pad\pad\pad\pad\pad\pad\pad\pad\pad\pad\pad\pad\pad\pad\pad
+.endm
+
+// 1000x 'a'
+pad_sections aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
+
+
+// /1000029 == 4 + 10 + (5 * (2 + (20 * 10 * 1000) + 1))
+//             v   |     |    v    ~~~~~~~~~~~~~~    v
+//    table size   v     v   "p0"        pad         NUL seperator
+//     "s12345678\0"     # of pad sections
+//
+// CHECK:   Section {
+// CHECK:     Number: 9
+// CHECK:     Name: seven_digit (2F 31 30 30 30 30 32 39)
+// CHECK:   }
+.section seven_digit; .long 1