digitalmars.D.learn - GC-less tutorial?
- Tove (7/7) Apr 07 2012 Hi,
- Jacob Carlborg (5/11) Apr 07 2012 The GC is plugable at link time, just remove it and you'll get linker
- Artur Skawina (33/38) Apr 07 2012 One problem with this is that the runtime wants to alloc some things bef...
- Tove (4/61) Apr 08 2012 great, thanks for the hint, I didn't think of using breakpoints
Hi, are there any good tutorials for using D totally without GC, detailing some common pitfalls? One thing on my wishlist would be a way to detect accidental GC allocations resulting from side-effects of every-day operations... generating linking errors would be sufficient for detecting this...
Apr 07 2012
Jacob Carlborg <doob me.com> On 2012-04-07 17:25, Tove wrote:Hi, are there any good tutorials for using D totally without GC, detailing some common pitfalls? One thing on my wishlist would be a way to detect accidental GC allocations resulting from side-effects of every-day operations... generating linking errors would be sufficient for detecting this...The GC is plugable at link time, just remove it and you'll get linker errors when it's used. -- /Jacob Carlborg
Apr 07 2012
On 04/07/12 17:25, Tove wrote:Hi, are there any good tutorials for using D totally without GC, detailing some common pitfalls? One thing on my wishlist would be a way to detect accidental GC allocations resulting from side-effects of every-day operations... generating linking errors would be sufficient for detecting this...One problem with this is that the runtime wants to alloc some things before your code gets to run - so you can't just remove the functions from the build. You're left with either modifying the runtime or somehow ignoring the initial allocations (which usually won't cause any problems). If using a custom RT would have been an option you wouldn't be asking these questions (as you could just omit the symbols), so... If your platform supports gdb, try creating a text file "trapallocs" containing: b gc_malloc b gc_qalloc b gc_calloc b gc_realloc b gc_extend then run "gdb -x ./trapallocs -ex run --args ./your_app" The debugger will stop at the first allocation and you can then use "bt" to check what's going on, then "c" to skip to the next alloc. The first few will come from the runtime and various module ctors, but anything after that will be caused by your code, directly or indirectly. You can also trap just the array ops with eg: b _d_arraycatT b _d_arraycatnT b _d_arrayappendT b _d_arrayappendcTp b _d_newarrayT etc Once the runtime becomes a shared library simpler solutions will be possible, but, until then, it doesn't get much better than this. You need some way to determine which allocations are "legal" and which are not; doing this w/o a custom runtime is probably not worth the effort... And, yes, the initial runtime allocations could (and should) me made to use a different path; some of them shouldn't happen at all. For example std.datetime alone causes two allocs via _d_newclass, in every D app that imports std.stdio... artur
Apr 07 2012
On Saturday, 7 April 2012 at 17:31:02 UTC, Artur Skawina wrote:On 04/07/12 17:25, Tove wrote:great, thanks for the hint, I didn't think of using breakpoints at first... but you are right, given good enough unit tests, the coverage would be sufficient!Hi, are there any good tutorials for using D totally without GC, detailing some common pitfalls? One thing on my wishlist would be a way to detect accidental GC allocations resulting from side-effects of every-day operations... generating linking errors would be sufficient for detecting this...One problem with this is that the runtime wants to alloc some things before your code gets to run - so you can't just remove the functions from the build. You're left with either modifying the runtime or somehow ignoring the initial allocations (which usually won't cause any problems). If using a custom RT would have been an option you wouldn't be asking these questions (as you could just omit the symbols), so... If your platform supports gdb, try creating a text file "trapallocs" containing: b gc_malloc b gc_qalloc b gc_calloc b gc_realloc b gc_extend then run "gdb -x ./trapallocs -ex run --args ./your_app" The debugger will stop at the first allocation and you can then use "bt" to check what's going on, then "c" to skip to the next alloc. The first few will come from the runtime and various module ctors, but anything after that will be caused by your code, directly or indirectly. You can also trap just the array ops with eg: b _d_arraycatT b _d_arraycatnT b _d_arrayappendT b _d_arrayappendcTp b _d_newarrayT etc Once the runtime becomes a shared library simpler solutions will be possible, but, until then, it doesn't get much better than this. You need some way to determine which allocations are "legal" and which are not; doing this w/o a custom runtime is probably not worth the effort... And, yes, the initial runtime allocations could (and should) me made to use a different path; some of them shouldn't happen at all. For example std.datetime alone causes two allocs via _d_newclass, in every D app that imports std.stdio... artur
Apr 08 2012