[lld] [LLD] Add CLASS syntax to SECTIONS (PR #95323)

[Peter Smith via llvm-commits]

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+# REQUIRES: x86
+
+# RUN: rm -rf %t && split-file %s %t && cd %t
+
+# RUN: llvm-mc -n -filetype=obj -triple=x86_64 matching.s -o matching.o
+
+## CLASS definitions match sections in linker script order. The sections may be
+## placed in a different order. Classes may derive from one another, and class
+## references may be restricted by INPUT_SECTION_FLAGS.
+
+# RUN: ld.lld -T matching.ld matching.o -o matching
+# RUN: llvm-readobj -x .rodata matching | FileCheck %s --check-prefix=MATCHING
+
+# MATCHING: 02030104
+
+
+## An error is reported when a section class has more than one description.
+
+# RUN: not ld.lld -T already-defined.ld matching.o 2>&1 | \
+# RUN:   FileCheck %s --check-prefix=ALREADY-DEFINED --implicit-check-not=error:
+
+# ALREADY-DEFINED: error: already-defined.ld:3: section class 'a' already defined
+
+
+## An error is reported when a filename pattern is missing in a section class
+## description.
+
+# RUN: not ld.lld -T missing-filename-pattern.ld matching.o 2>&1 | \
+# RUN:   FileCheck %s --check-prefix=MISSING-FILENAME-PATTERN --implicit-check-not=error:
+
+# MISSING-FILENAME-PATTERN: error: missing-filename-pattern.ld:2: expected filename pattern
+
+
+## An error is reported when the content of section classes is demanded before
+## input sections have been assigned to them.
+
+# RUN: not ld.lld -T used-before-assigned.ld matching.o 2>&1 | \
+# RUN:   FileCheck %s --check-prefix=USED-BEFORE-ASSIGNED
+
+# USED-BEFORE-ASSIGNED: error: section class 'a' used before assigned
----------------
smithp35 wrote:

I'm wondering if assigned is the best word here. I intuitively thought of CLASS (a) { ... } as defining CLASS (a). With input sections assigned to class 'a'.

If we know what output section we are in, it could be worth mentioning that.

Perhaps "section class 'a' assigned to output section 's' before definition of class.

https://github.com/llvm/llvm-project/pull/95323