chromium/third_party/dpkg-shlibdeps/patches/0001-dkpg-shlibdeps-add-option-to-ignore-weak-undefined-symbols.patch

From 59477dae6f2c68f0ebd9ccca18e737b67408bc11 Mon Sep 17 00:00:00 2001
From: Tom Anderson <[email protected]>
Date: Wed, 8 Jan 2020 10:55:20 -0800
Subject: [PATCH 1/2] dkpg-shlibdeps: Add option to ignore weak undefined
 symbols

Weak undefined symbols can be used to test feature support. For example:

__attribute__((weak)) uint64_t gbm_bo_get_modifier(struct gbm_bo* bo);
void foo(gbm_bo* bo) {
    // gbm_create_device is a strong undefined symbol. The dynamic linker will
    // fail if this is not available.
    gbm_create_device(1234);
    // gbm_bo_get_modifier is a weak undefined symbol. It will be NULL if it's
    // not available.
    if (gbm_bo_get_modifier)
        gbm_bo_get_modifier(bo);
}

However currently, dpkg-shlibdeps would consider gbm_bo_get_modifier in the
example to be a required symbol (and would increase the minimum required library
version), even though the intention is to use it only if it is available.

To address this, this change skips weak undefined symbols when checking for
dependencies. Out of an abundance of caution, this behavior is guarded behind a
new flag: --ignore-weak-undefined.
---
 scripts/dpkg-shlibdeps.pl | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/scripts/dpkg-shlibdeps.pl b/scripts/dpkg-shlibdeps.pl
index 8142c85b4..e3d8c7200 100755
--- a/scripts/dpkg-shlibdeps.pl
+++ b/scripts/dpkg-shlibdeps.pl
@@ -67,6 +67,7 @@ my $varlistfile = 'debian/substvars';
 my $varlistfilenew;
 my $varnameprefix = 'shlibs';
 my $ignore_missing_info = 0;
+my $ignore_weak_undefined = 0;
 my $warnings = WARN_SYM_NOT_FOUND | WARN_DEP_AVOIDABLE;
 my $debug = 0;
 my @exclude = ();
@@ -120,6 +121,8 @@ foreach (@ARGV) {
 	}
     } elsif (m/^--ignore-missing-info$/) {
 	$ignore_missing_info = 1;
+    } elsif (m/^--ignore-weak-undefined$/) {
+	$ignore_weak_undefined = 1;
     } elsif (m/^--warnings=(\d+)$/) {
 	$warnings = $1;
     } elsif (m/^-t(.*)$/) {
@@ -365,6 +368,7 @@ foreach my $file (keys %exec) {
     }
     debug(2, 'Analyzing all undefined symbols');
     foreach my $sym ($obj->get_undefined_dynamic_symbols()) {
+	next if $ignore_weak_undefined && $sym->{weak};
 	my $name = $sym->{name};
 	if ($sym->{version}) {
 	    $name .= '@' . "$sym->{version}";
@@ -610,6 +614,8 @@ sub usage {
                              in the given build directory.
   -v                       enable verbose mode (can be used multiple times).
   --ignore-missing-info    don't fail if dependency information can't be found.
+  --ignore-weak-undefined  only allow strong undefined symbols to introduce
+                             dependencies.
   --warnings=<value>       define set of active warnings (see manual page).
   --admindir=<directory>   change the administrative directory.
   -?, --help               show this help message.
-- 
2.25.0.rc1.283.g88dfdc4193-goog