This part of the wiki collects all the information related to debugging GHC. That includes debugging the compiler itself, the libraries, the runtime system, the code generator, or the build system.
- If you're debugging a compiler panic or some problem in GHC itself, then go to Debugging/Compiler
- If the compiled program crashes or panics, then go to Debugging/CompiledCode
- For debugging the runtime system, see Debugging/RuntimeSystem
- For debugging when running under GHCi, see Commentary/Compiler/Backends/GHCi
- Performance debugging.
- Debugging/ProfilingGhc: Profiling the compiler itself.
- Debugging/TickyTicky: for debugging performance-related issues in compiled code. Typically for performance debugging of the Simplifier and Core-level optimisations.
- Debugging/LowLevelProfiling: way to investigate low-level performance, typically for performance debugging of the code generator or RTS.
- Build failures. If you're trying to debug a build failure, then you probably want to look at
- Use count_lines to count the number of lines of code in the compiler
- Use compareSizes to compare the sizes of corresponding .o or .hi files in two trees.
- If know the last good commit, bisection may be useful to identify which commit introduced the bug.
The count_lines script, which is put in $(TOP)/inplace/bin, counts source lines and comments. The command-line arguments are the Haskell source files to count.
bash-3.2$ $head/count_lines compiler/*/*hs Code Comments compiler/basicTypes 4565 5092 compiler/cmm 9685 4703 ... compiler/utils 6316 4669 compiler/vectorise 2608 669 TOTAL: 105893 86247 Code Comments Annotations.lhs 57 44 AsmCodeGen.lhs 591 333 Bag.lhs 140 51 .... ZipCfgExtras.hs 43 33 ZipDataflow.hs 779 271 TOTAL: 105893 86247
The source for count_lines is in $(TOP)/utils/count_lines.
The compareSizes program compares the sizes of corresponding files in two trees:
$ ./compareSizes --hi ~/ghc/darcs/ghc ~/ghc/6.12-branch/ghc Size | Change | Filename 25644 | -0.99% | compiler/stage1/build/Demand.hi 21103 | -0.98% | compiler/stage2/build/Demand.hi 180044 | -0.98% | libraries/base/dist-install/build/GHC/Classes.hi 6415 | -0.58% | .../Data/Array/Parallel/Prelude/Base/Tuple.hi 6507 | -0.57% | .../Data/Array/Parallel/Prelude/Base/Tuple.hi [...] 3264 | 3.16% | .../Parallel/Unlifted/Sequential/Flat/Enum.hi 51389 | 3.30% | .../build/Language/Haskell/Extension.hi 1415 | 72.18% | libraries/base/dist-install/build/Data/Tuple.hi 28752162 | -0.00% | TOTAL
- --o to compare object files.
- --hi to compare interface files [DEFAULT]
There's a hack to avoid descending into '*_split' directories.
The source for compareSizes is in $(TOP)/utils/compare_sizes.