aix: Add weak symbol detection ...

in create_expfile.sh

AIX export files support the `weak` keyword to mark weak symbols.
ref: https://www.ibm.com/docs/en/aix/7.2.0?topic=l-ld-command#ld__a3119106d

This helps preserve C++ weak symbol semantics and preventing potential linker conflicts.

Author: abmusse

tools/create_expfile.sh

@@ -5,60 +5,79 @@
 # specifically for export so that they can be used
 # by native add-ons.
 #
-# The raw symbol data is obtained by using nm on
+# The raw symbol data is obtained by using dump -tov on
 # the .a files which make up the node executable.
 #
-# -Xany processes symbols for both 32-bit and
-# 64-bit (the default is for 32-bit only).
+# dump -tov flags:
+# -t: Display symbol table entries
+# -o: Display object file headers
+# -v: Display visibility information (HIDDEN/EXPORTED/PROTECTED)
+# -X 32_64: Process both 32-bit and 64-bit symbols
 #
-# -g selects only exported symbols.
+# This approach is similar to CMake's ExportImportList module for AIX:
+# https://github.com/Kitware/CMake/blob/45f4742cbfe6c25c7c801e3806c8af04a2c4b09b/Modules/Platform/AIX/ExportImportList#L67-L80
 #
-# -C, -B and -p ensure that the output is in a
-# format that can be easily parsed and converted
-# into the required symbol.
-#
-# -C suppresses the demangling of C++ names.
-# -B writes the output in BSD format.
-# -p displays the info in a standard portable
-#    output format.
-#
-# Only include symbols if they are of the following
-# types and don't start with a dot.
-#
-# T - Global text symbol.
-# D - Global data symbol.
-# B - Global bss symbol.
+# We filter for symbols in .text, .data, .tdata, and .bss sections
+# with extern or weak linkage, excluding:
+# - Symbols starting with dot (internal/local symbols)
+# - __sinit/__sterm (static initialization/termination)
+# - __[0-9]+__ (compiler-generated symbols)
+# - HIDDEN visibility symbols (to avoid linker error 0711-407)
 #
 # The final sort allows removal of any duplicates.
 #
 # Symbols for the gtest libraries are excluded as
 # they are not linked into the node executable.
 #
-set -x
 echo "Searching $1 to write out expfile to $2"
 
 # This special sequence must be at the start of the exp file.
 echo "#!." > "$2.tmp"
 
 # Pull the symbols from the .a files.
-# Use dump -tov to get visibility information and exclude HIDDEN symbols
+# Use dump -tov to get visibility information and exclude HIDDEN symbols.
 # This prevents AIX linker error 0711-407 when addons try to import symbols
 # with visibility attributes.
+#
+# IMPORTANT: AIX dump -tov output has a visibility column that contains either
+# a visibility keyword (HIDDEN/EXPORTED/PROTECTED) or blank spaces when no
+# visibility attribute is set. Since AWK splits fields on whitespace, this
+# results in different field counts:
+#
+# With visibility keyword (8 fields after AWK splits):
+#   [137] m 0x00003290 .text 1 weak HIDDEN ._ZNKSt3__1...
+#    $1  $2    $3      $4   $5  $6    $7        $8
+#                              |     |         └─ Symbol name
+#                              |     └─ Visibility (HIDDEN/EXPORTED/PROTECTED)
+#                              └─ Linkage (weak/extern)
+#
+# Without visibility keyword (7 fields after AWK splits, spaces collapsed):
+#   [77] m 0x00000000 .text 1 weak ._ZN8simdjson...
+#    $1 $2    $3      $4   $5  $6       $7
+#                             |         └─ Symbol name
+#                             └─ Linkage (weak/extern)
+#
+# The awk script handles both cases by using an associative array V[]
+# to map field values to their export suffixes. For fields that don't match
+# any key in V[], the lookup returns an empty string, which is perfect for
+# handling the variable field positions caused by the blank visibility column.
+#
 find "$1" -name "*.a" | grep -v gtest | while read f; do
     dump -tov -X 32_64 "$f" 2>/dev/null | \
     awk '
         BEGIN {
             V["EXPORTED"]=" export"
             V["PROTECTED"]=" protected"
             V["HIDDEN"]=" hidden"
+            V["weak"]=" weak"
         }
-        /^\[[0-9]+\]\tm +[^ ]+ +\.(text|data|tdata|bss) +[^ ]+ +(extern|weak) +(EXPORTED|PROTECTED|HIDDEN| ) / {
+        /^\[[0-9]+\]\tm +[^ ]+ +\.(text|data|tdata|bss) +[^ ]+ +(extern|weak)( +(EXPORTED|PROTECTED|HIDDEN))?/ {
             # Exclude symbols starting with dot, __sinit, __sterm, __[0-9]+__
             # Also exclude HIDDEN symbols to avoid visibility attribute issues
             if (!match($NF,/^(\.|__sinit|__sterm|__[0-9]+__)/)) {
-                visibility = $(NF-1)
-                if (visibility != "HIDDEN") {
-                    print $NF
+                # Skip if HIDDEN visibility (can be at $(NF-1) or $(NF-2))
+                if ($(NF-1) != "HIDDEN" && $(NF-2) != "HIDDEN") {
+                    print $NF V[$(NF-1)] V[$(NF-2)]
                 }
             }
         }