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
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
compiler/basicTypes 4565 5092
compiler/cmm 9685 4703
compiler/utils 6316 4669
compiler/vectorise 2608 669
TOTAL: 105893 86247
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
There's a hack to avoid descending into '*_split' directories.
The source for compareSizes is in $(TOP)/utils/compare_sizes.