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authorMatt A. Tobin <mattatobin@localhost.localdomain>2018-02-02 04:16:08 -0500
committerMatt A. Tobin <mattatobin@localhost.localdomain>2018-02-02 04:16:08 -0500
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+lldb debugging functionality for Gecko
+======================================
+
+This directory contains a module, lldbutils, which is imported by the
+in-tree .lldbinit file. The lldbutil modules define some lldb commands
+that are handy for debugging Gecko.
+
+If you want to add a new command or Python-implemented type summary, either add
+it to one of the existing broad area Python files (such as lldbutils/layout.py
+for layout-related commands) or create a new file if none of the existing files
+is appropriate. If you add a new file, make sure you add it to __all__ in
+lldbutils/__init__.py.
+
+
+Supported commands
+------------------
+
+Most commands below that can take a pointer to an object also support being
+called with a smart pointer like nsRefPtr or nsCOMPtr.
+
+
+* frametree EXPR, ft EXPR
+ frametreelimited EXPR, ftl EXPR
+
+ Shows information about a frame tree. EXPR is an expression that
+ is evaluated, and must be an nsIFrame*. frametree displays the
+ entire frame tree that contains the given frame. frametreelimited
+ displays a subtree of the frame tree rooted at the given frame.
+
+ (lldb) p this
+ (nsBlockFrame *) $4 = 0x000000011687fcb8
+ (lldb) ftl this
+ Block(div)(-1)@0x11687fcb8 {0,0,7380,690} [state=0002100000d04601] [content=0x11688c0c0] [sc=0x11687f990:-moz-scrolled-content]<
+ line 0x116899130: count=1 state=inline,clean,prevmarginclean,not impacted,not wrapped,before:nobr,after:nobr[0x100] {60,0,0,690} vis-overflow=60,510,0,0 scr-overflow=60,510,0,0 <
+ Text(0)""@0x1168990c0 {60,510,0,0} [state=0001000020404000] [content=0x11687ca10] [sc=0x11687fd88:-moz-non-element,parent=0x11687eb00] [run=0x115115e80][0,0,T]
+ >
+ >
+ (lldb) ft this
+ Viewport(-1)@0x116017430 [view=0x115efe190] {0,0,60,60} [state=000b063000002623] [sc=0x1160170f8:-moz-viewport]<
+ HTMLScroll(html)(-1)@0x1160180d0 {0,0,0,0} [state=000b020000000403] [content=0x115e4d640] [sc=0x116017768:-moz-viewport-scroll]<
+ ...
+ Canvas(html)(-1)@0x116017e08 {0,0,60,60} vis-overflow=0,0,8340,2196 scr-overflow=0,0,8220,2196 [state=000b002000000601] [content=0x115e4d640] [sc=0x11687e0f8:-moz-scrolled-canvas]<
+ Block(html)(-1)@0x11687e578 {0,0,60,2196} vis-overflow=0,0,8340,2196 scr-overflow=0,0,8220,2196 [state=000b100000d00601] [content=0x115e4d640] [sc=0x11687e4b8,parent=0x0]<
+ line 0x11687ec48: count=1 state=block,clean,prevmarginclean,not impacted,not wrapped,before:nobr,after:nobr[0x48] bm=480 {480,480,0,1236} vis-overflow=360,426,7980,1410 scr-overflow=480,480,7740,1236 <
+ Block(body)(1)@0x11687ebb0 {480,480,0,1236} vis-overflow=-120,-54,7980,1410 scr-overflow=0,0,7740,1236 [state=000b120000100601] [content=0x115ed8980] [sc=0x11687e990]<
+ line 0x116899170: count=1 state=inline,clean,prevmarginclean,not impacted,not wrapped,before:nobr,after:nobr[0x0] {0,0,7740,1236} vis-overflow=-120,-54,7980,1410 scr-overflow=0,0,7740,1236 <
+ nsTextControlFrame@0x11687f068 {0,66,7740,1170} vis-overflow=-120,-120,7980,1410 scr-overflow=0,0,7740,1170 [state=0002000000004621] [content=0x115ca2c50] [sc=0x11687ea40]<
+ HTMLScroll(div)(-1)@0x11687f6b0 {180,240,7380,690} [state=0002000000084409] [content=0x11688c0c0] [sc=0x11687eb00]<
+ Block(div)(-1)@0x11687fcb8 {0,0,7380,690} [state=0002100000d04601] [content=0x11688c0c0] [sc=0x11687f990:-moz-scrolled-content]<
+ line 0x116899130: count=1 state=inline,clean,prevmarginclean,not impacted,not wrapped,before:nobr,after:nobr[0x100] {60,0,0,690} vis-overflow=60,510,0,0 scr-overflow=60,510,0,0 <
+ Text(0)""@0x1168990c0 {60,510,0,0} [state=0001000020404000] [content=0x11687ca10] [sc=0x11687fd88:-moz-non-element,parent=0x11687eb00] [run=0x115115e80][0,0,T]
+ ...
+
+
+* js
+
+ Dumps the current JS stack.
+
+ (lldb) js
+ 0 anonymous(aForce = false) ["chrome://browser/content/browser.js":13414]
+ this = [object Object]
+ 1 updateAppearance() ["chrome://browser/content/browser.js":13326]
+ this = [object Object]
+ 2 handleEvent(aEvent = [object Event]) ["chrome://browser/content/tabbrowser.xml":3811]
+ this = [object XULElement]
+
+
+* prefcnt EXPR
+
+ Shows the refcount of a given object. EXPR is an expression that is
+ evaluated, and can be either a pointer to or an actual refcounted
+ object. The object can be a standard nsISupports-like refcounted
+ object, a cycle-collected object or a mozilla::RefCounted<T> object.
+
+ (lldb) p this
+ (nsHTMLDocument *) $1 = 0x0000000116e9d800
+ (lldb) prefcnt this
+ 20
+ (lldb) p mDocumentURI
+ (nsCOMPtr<nsIURI>) $3 = {
+ mRawPtr = 0x0000000117163e50
+ }
+ (lldb) prefcnt mDocumentURI
+ 11
+
+
+* pstate EXPR
+
+ Shows the frame state bits (using their symbolic names) of a given frame.
+ EXPR is an expression that is evaluated, and must be an nsIFrame*.
+
+ (lldb) p this
+ (nsTextFrame *) $1 = 0x000000011f470b10
+ (lldb) p/x mState
+ (nsFrameState) $2 = 0x0000004080604000
+ (lldb) pstate this
+ TEXT_HAS_NONCOLLAPSED_CHARACTERS | TEXT_END_OF_LINE | TEXT_START_OF_LINE | NS_FRAME_PAINTED_THEBES | NS_FRAME_INDEPENDENT_SELECTION
+
+
+* ptag EXPR
+
+ Shows the DOM tag name of a node. EXPR is an expression that is
+ evaluated, and can be either an nsINode pointer or a concrete DOM
+ object.
+
+ (lldb) p this
+ (nsHTMLDocument *) $0 = 0x0000000116e9d800
+ (lldb) ptag this
+ (PermanentAtomImpl *) $1 = 0x0000000110133ac0 u"#document"
+ (lldb) p this->GetRootElement()
+ (mozilla::dom::HTMLSharedElement *) $2 = 0x0000000118429780
+ (lldb) ptag $2
+ (PermanentAtomImpl *) $3 = 0x0000000110123b80 u"html"
+
+
+Supported type summaries and synthetic children
+-----------------------------------------------
+
+In lldb terminology, type summaries are rules for how to display a value
+when using the "expression" command (or its familiar-to-gdb-users "p" alias),
+and synthetic children are fake member variables or array elements also
+added by custom rules.
+
+For objects that do have synthetic children defined for them, like nsTArray,
+the "expr -R -- EXPR" command can be used to show its actual member variables.
+
+
+* nsAString, nsACString,
+ nsFixedString, nsFixedCString,
+ nsAutoString, nsAutoCString
+
+ Strings have a type summary that shows the actual string.
+
+ (lldb) frame info
+ frame #0: 0x000000010400cfea XUL`nsCSSParser::ParseProperty(this=0x00007fff5fbf5248, aPropID=eCSSProperty_margin_top, aPropValue=0x00007fff5fbf53f8, aSheetURI=0x0000000115ae8c00, aBaseURI=0x0000000115ae8c00, aSheetPrincipal=0x000000010ff9e040, aDeclaration=0x00000001826fd580, aChanged=0x00007fff5fbf5247, aIsImportant=false, aIsSVGMode=false) + 74 at nsCSSParser.cpp:12851
+ (lldb) p aPropValue
+ (const nsAString_internal) $16 = u"-25px"
+
+ (lldb) p this
+ (nsHTMLDocument *) $18 = 0x0000000115b56000
+ (lldb) p mContentType
+ (nsCString) $19 = {
+ nsACString_internal = "text/html"
+ }
+
+* nscolor
+
+ nscolors (32-bit RGBA colors) have a type summary that shows the color as
+ one of the CSS 2.1 color keywords, a six digit hex color, an rgba() color,
+ or the "transparent" keyword.
+
+ (lldb) p this
+ (nsTextFrame *) $0 = 0x00000001168245e0
+ (lldb) p *this->StyleColor()
+ (const nsStyleColor) $1 = {
+ mColor = lime
+ }
+ (lldb) expr -R -- *this->StyleColor()
+ (const nsStyleColor) $2 = {
+ mColor = 4278255360
+ }
+
+* nsIAtom
+
+ Atoms have a type summary that shows the string value inside the atom.
+
+ (lldb) frame info
+ frame #0: 0x00000001028b8c49 XUL`mozilla::dom::Element::GetBoolAttr(this=0x0000000115ca1c50, aAttr=0x000000011012a640) const + 25 at Element.h:907
+ (lldb) p aAttr
+ (PermanentAtomImpl *) $1 = 0x000000011012a640 u"readonly"
+
+* nsTArray and friends
+
+ nsTArrays and their auto and fallible varieties have synthetic children
+ for their elements. This means when displaying them with "expr" (or "p"),
+ they will be shown like regular arrays, rather than showing the mHdr and
+ other fields.
+
+ (lldb) frame info
+ frame #0: 0x00000001043eb8a8 XUL`SVGTextFrame::DoGlyphPositioning(this=0x000000012f3f8778) + 248 at SVGTextFrame.cpp:4940
+ (lldb) p charPositions
+ (nsTArray<nsPoint>) $5 = {
+ [0] = {
+ mozilla::gfx::BasePoint<int, nsPoint> = {
+ x = 0
+ y = 816
+ }
+ }
+ [1] = {
+ mozilla::gfx::BasePoint<int, nsPoint> = {
+ x = 426
+ y = 816
+ }
+ }
+ [2] = {
+ mozilla::gfx::BasePoint<int, nsPoint> = {
+ x = 906
+ y = 816
+ }
+ }
+ }
+ (lldb) expr -R -- charPositions
+ (nsTArray<nsPoint>) $4 = {
+ nsTArray_Impl<nsPoint, nsTArrayInfallibleAllocator> = {
+ nsTArray_base<nsTArrayInfallibleAllocator, nsTArray_CopyWithMemutils> = {
+ mHdr = 0x000000012f3f1b80
+ }
+ }
+ }
+
+* nsTextNode, nsTextFragment
+
+ Text nodes have a type summary that shows the nsTextFragment in the
+ nsTextNode, which itself has a type summary that shows the text
+ content.
+
+ (lldb) p this
+ (nsTextFrame *) $14 = 0x000000011811bb10
+ (lldb) p mContent
+ (nsTextNode *) $15 = 0x0000000118130110 "Search or enter address"
+