Meson/Linux: parse the malloc.cpp source instead of malloc.cpp.o

I want to avoid having to build the .o file before extracting malloc.o
from libc.a. To parse the source file, we need a clear marker, which I
also used to avoid having to have duplicate declarations.

Because of Meson is incapable of using backslashes in custom_target()
commands (see [1]), I had to write a shell script to execute sed, so I
decided to move the ar x command there too.

[1] mesonbuild/meson#1564

Signed-off-by: Thiago Macieira <[email protected]>

framework/sysdeps/linux/extract-malloc.sh

@@ -0,0 +1,46 @@
+#!/bin/bash -e
+# Copyright 2023 Intel Corporation.
+# SPDX-License-Identifier: Apache-2.0
+#
+while [[ "$1" = *=* ]]; do
+    # Evaluate variable assignments, like AR= and OBJCOPY=
+    eval "$1"
+    shift
+done
+if [[ "$1" = "--" ]]; then
+    shift
+fi
+
+if [[ $# -lt 3 ]]; then
+    cat <<EOF
+Extracts malloc.o from static libc and localizes symbols defined in malloc.cpp.
+Syntax:
+    $0 [variable-assignments] /path/to/libc.a /path/to/malloc.cpp /path/to/output/malloc.o
+Variable assignments can be:
+  AR=/path/to/ar
+EOF
+    exit 0
+fi
+
+# Positional arguments
+libc_a=$1
+malloc_cpp=$2
+output=$3
+output_dirname=${output%/*}
+output_basename=${output##*/}
+
+# Define $AR and $OBJCOPY if they aren't defined.
+: ${AR:=ar}
+: ${OBJCOPY:=objcopy}
+
+# Generate the -L arguments based on DECLARE_OVERRIDE inside malloc.cpp
+objcopy_args=(`sed -En "/^DECLARE_OVERRIDE\((\w+)\).*/s//-L\1/p" "$malloc_cpp"`)
+
+# Extract malloc.o from libc.a
+"$AR" x --output "$output_dirname" "$libc_a" malloc.o
+
+# Rename if necessary
+[[ "$output_basename" = malloc.o ]] || mv -- "$output_dirname/malloc.o" "$output"
+
+# Transform it
+"$OBJCOPY" "${objcopy_args[@]}" "$output"

framework/sysdeps/linux/malloc.cpp

@@ -30,14 +30,19 @@
 #  endif
 
 extern "C" {
-extern void *__libc_memalign(size_t alignment, size_t size);
-extern int __libc_posix_memalign (void **memptr, size_t alignment, size_t size);
-extern void *__libc_memalign (size_t alignment, size_t bytes);
-extern void *__libc_valloc (size_t bytes);
-extern void *__libc_pvalloc (size_t bytes);
-extern void *__libc_calloc (size_t n, size_t elem_size);
-extern void *__libc_malloc(size_t size);
-extern void *__libc_realloc (void *oldmem, size_t bytes);
+#define DECLARE_OVERRIDE(FUNC)  extern decltype(FUNC) __libc_ ## FUNC
+
+// The following lines are parsed by the buildsystem, so be careful when
+// modifying them. See extract-malloc.sh.
+DECLARE_OVERRIDE(calloc);
+DECLARE_OVERRIDE(malloc);
+DECLARE_OVERRIDE(memalign);
+DECLARE_OVERRIDE(posix_memalign);
+DECLARE_OVERRIDE(pvalloc);
+DECLARE_OVERRIDE(realloc);
+DECLARE_OVERRIDE(valloc);
+
+#undef DECLARE_OVERRIDE
 }
 
 static void *bzero_block(void *ptr, size_t len)

framework/sysdeps/linux/meson.build

@@ -42,35 +42,30 @@ _sysdeps_a = static_library(
 
 if get_option('cpp_link_args').contains('-static')
     ar = find_program('ar')
-    nm = find_program('nm')
     objcopy = find_program('objcopy')
 
     # Need to extract malloc.o from libc.a and transform it
-    # Step 1: extract it:
+    # Step 1: find libc.a by asking the compiler
     libc_a = run_command(cc.cmd_array(), '-print-file-name=libc.a',
            check: true
     )
 
-    orig_glibc_malloc_o = custom_target(
-        'extract-malloc.o',
-        output: 'malloc.o',
-        input: libc_a.stdout().strip(),
-        command: [
-            ar, 'x', '--output', '@OUTDIR@', '@INPUT@', '@OUTPUT@',
-        ]
-    )
-    # Step 2: transform it by localizing (-L) all the symbols from our malloc.cpp
+    # Step 2: run our extractor script
     glibc_malloc_o = custom_target(
         'glibc_malloc.o',
         input: [
-            _sysdeps_a.extract_objects('malloc.cpp'),
-            orig_glibc_malloc_o,
+            libc_a.stdout().strip(),
+            files('malloc.cpp'),
         ],
         output: 'glibc_malloc.o',
         command: [
-            shell, '-c', objcopy.full_path() + ' `' +
-            nm.full_path() + ' --defined $0 | sed -En "/^.* T /s//-L /p"` $1 $2',
-            '@INPUT@', '@OUTPUT@',
+            shell,
+            files('extract-malloc.sh'),
+            'AR=' + ar.full_path(),
+            'OBJCOPY=' + objcopy.full_path(),
+            '--',
+            '@INPUT@',
+            '@OUTPUT@',
         ]
     )
     # Step 3: add this file to the sysdeps library