avoid using global PendingError to avoid failing too often too soon

Our error reporting is historically grown into some kind of mess.
A while ago I implemented stacking for the global error which is used in
this commit now to wrap calls to functions which do not report (all)
errors via return, so that only failures in those calls cause a failure
to propergate down the chain rather than failing if anything
(potentially totally unrelated) has failed at some point in the past.

This way we can avoid stopping the entire acquire process just because a
single source produced an error for example. It also means that after
the acquire process the cache is generated – even if the acquire
process had failures – as we still have the old good data around we can and
should generate a cache for (again).

There are probably more instances of this hiding, but all these looked
like the easiest to work with and fix with reasonable (aka net-positive)
effects.

4 files changed, 23 insertions, 25 deletions

diff --git a/apt-pkg/contrib/error.cc b/apt-pkg/contrib/error.cc
index 892cd4874..8a87e16e9 100644
--- a/apt-pkg/contrib/error.cc
+++ b/apt-pkg/contrib/error.cc
@@ -27,6 +27,7 @@
 #include <unistd.h>
 #include <string>
 #include <cstring>
+#include <algorithm>
 
 									/*}}}*/
 
@@ -212,12 +213,13 @@ void GlobalError::DumpErrors(std::ostream &out, MsgType const &threshold,
 	if (mergeStack == true)
 		for (std::list<MsgStack>::const_reverse_iterator s = Stacks.rbegin();
 		     s != Stacks.rend(); ++s)
-			Messages.insert(Messages.begin(), s->Messages.begin(), s->Messages.end());
+			std::copy(s->Messages.begin(), s->Messages.end(), std::front_inserter(Messages));
+
+	std::for_each(Messages.begin(), Messages.end(), [&threshold, &out](Item const &m) {
+		if (m.Type >= threshold)
+			out << m << std::endl;
+	});
 
-	for (std::list<Item>::const_iterator m = Messages.begin();
-	     m != Messages.end(); ++m)
-		if (m->Type >= threshold)
-			out << (*m) << std::endl;
 	Discard();
 }
 									/*}}}*/
@@ -228,25 +230,21 @@ void GlobalError::Discard() {
 }
 									/*}}}*/
 // GlobalError::empty - does our error list include anything?		/*{{{*/
-bool GlobalError::empty(MsgType const &trashhold) const {
+bool GlobalError::empty(MsgType const &threshold) const {
 	if (PendingFlag == true)
 		return false;
 
 	if (Messages.empty() == true)
 		return true;
 
-	for (std::list<Item>::const_iterator m = Messages.begin();
-	     m != Messages.end(); ++m)
-		if (m->Type >= trashhold)
-			return false;
-
-	return true;
+	return std::find_if(Messages.begin(), Messages.end(), [&threshold](Item const &m) {
+		return m.Type >= threshold;
+	}) == Messages.end();
 }
 									/*}}}*/
 // GlobalError::PushToStack						/*{{{*/
 void GlobalError::PushToStack() {
-	MsgStack pack(Messages, PendingFlag);
-	Stacks.push_back(pack);
+	Stacks.emplace_back(Messages, PendingFlag);
 	Discard();
 }
 									/*}}}*/
@@ -262,7 +260,7 @@ void GlobalError::RevertToStack() {
 // GlobalError::MergeWithStack						/*{{{*/
 void GlobalError::MergeWithStack() {
 	MsgStack pack = Stacks.back();
-	Messages.insert(Messages.begin(), pack.Messages.begin(), pack.Messages.end());
+	Messages.splice(Messages.begin(), pack.Messages);
 	PendingFlag = PendingFlag || pack.PendingFlag;
 	Stacks.pop_back();
 }
diff --git a/apt-pkg/contrib/error.h b/apt-pkg/contrib/error.h
index ed8c19153..1fb0ede4a 100644
--- a/apt-pkg/contrib/error.h
+++ b/apt-pkg/contrib/error.h
@@ -333,7 +333,7 @@ private:								/*{{{*/
 	bool PendingFlag;
 
 	struct MsgStack {
-		std::list<Item> const Messages;
+		std::list<Item> Messages;
 		bool const PendingFlag;
 
 		MsgStack(std::list<Item> const &Messages, bool const &Pending) :
diff --git a/apt-pkg/contrib/fileutl.cc b/apt-pkg/contrib/fileutl.cc
index 52fedce8f..02b27f5cf 100644
--- a/apt-pkg/contrib/fileutl.cc
+++ b/apt-pkg/contrib/fileutl.cc
@@ -665,7 +665,7 @@ string flAbsPath(string File)
    char *p = realpath(File.c_str(), NULL);
    if (p == NULL)
    {
-      _error->Errno("realpath", "flAbsPath failed");
+      _error->Errno("realpath", "flAbsPath on %s failed", File.c_str());
       return "";
    }
    std::string AbsPath(p);
diff --git a/apt-pkg/contrib/mmap.cc b/apt-pkg/contrib/mmap.cc
index b2a53a6cb..8e169027e 100644
--- a/apt-pkg/contrib/mmap.cc
+++ b/apt-pkg/contrib/mmap.cc
@@ -215,9 +215,6 @@ DynamicMMap::DynamicMMap(FileFd &F,unsigned long Flags,unsigned long const &Work
 		MMap(F,Flags | NoImmMap), Fd(&F), WorkSpace(Workspace),
 		GrowFactor(Grow), Limit(Limit)
 {
-   if (_error->PendingError() == true)
-      return;
-
    // disable Moveable if we don't grow
    if (Grow == 0)
       this->Flags &= ~Moveable;
@@ -252,9 +249,6 @@ DynamicMMap::DynamicMMap(unsigned long Flags,unsigned long const &WorkSpace,
 		MMap(Flags | NoImmMap | UnMapped), Fd(0), WorkSpace(WorkSpace),
 		GrowFactor(Grow), Limit(Limit)
 {
-	if (_error->PendingError() == true)
-		return;
-
 	// disable Moveable if we don't grow
 	if (Grow == 0)
 		this->Flags &= ~Moveable;
@@ -390,12 +384,15 @@ unsigned long DynamicMMap::Allocate(unsigned long ItemSize)
       const unsigned long size = 20*1024;
       I->Count = size/ItemSize;
       Pool* oldPools = Pools;
+      _error->PushToStack();
       Result = RawAllocate(size,ItemSize);
+      bool const newError = _error->PendingError();
+      _error->MergeWithStack();
       if (Pools != oldPools)
 	 I += Pools - oldPools;
 
       // Does the allocation failed ?
-      if (Result == 0 && _error->PendingError())
+      if (Result == 0 && newError)
 	 return 0;
       I->Start = Result;
    }
@@ -416,9 +413,12 @@ unsigned long DynamicMMap::WriteString(const char *String,
    if (Len == (unsigned long)-1)
       Len = strlen(String);
 
+   _error->PushToStack();
    unsigned long const Result = RawAllocate(Len+1,0);
+   bool const newError = _error->PendingError();
+   _error->MergeWithStack();
 
-   if (Base == NULL || (Result == 0 && _error->PendingError()))
+   if (Base == NULL || (Result == 0 && newError))
       return 0;
 
    memcpy((char *)Base + Result,String,Len);