[commit: ghc] master: Slighly clean up symbol loading error. (f41c27d)

[git at git.haskell.org]

Repository : ssh://git@git.haskell.org/ghc

On branch  : master
Link       : http://ghc.haskell.org/trac/ghc/changeset/f41c27d3ffdddbb1afe07de1bd25205061194c93/ghc

>---------------------------------------------------------------

commit f41c27d3ffdddbb1afe07de1bd25205061194c93
Author: Tamar Christina <tamar at zhox.com>
Date:   Mon Jan 30 11:58:19 2017 -0500

    Slighly clean up symbol loading error.
    
    The symbol not found error that is triggered
    during lazy-loading was a bit chaotic before.
    
    This reformats it a bit to:
    
    ```
    ghc-stage2.exe:  | E:\...\libLLVMSupport.a: unknown symbol `_ZN4llvm5APIntC1Ejyb'
    ghc-stage2.exe:  | E:\...\libLLVMCore.a: unknown symbol `_ZN4llvm5APInt14AssignSlowCaseERKS0_'
    ghc-stage2.exe:  | E:\...\libLLVMCore.a: unknown symbol `_ZN4llvm13ConstantRangeC1ENS_5APIntES1_'
    ghc-stage2.exe:  | E:\...\libLLVMCore.a: unknown symbol `_ZN4llvm14FoldingSetImplC2Ej'
    ghc-stage2.exe:  | E:\...\libLLVMCore.a: unknown symbol `_ZN4llvm15LLVMContextImplD1Ev'
    ghc-stage2.exe:  | E:\...\libLLVMLTO.a: unknown symbol `_ZN4llvm11LLVMContextD1Ev'
    ghc-stage2.exe:  | E:\...\libLLVMCore.a: unknown symbol `_ZNK4llvm5Value10getContextEv'
    ghc-stage2.exe: ^^ Could not load 'LLVMIsMultithreaded', dependency unresolved.
    See top entry above.
    ```
    
    I have also thought about also showing the demangled names, as it may
    be useful for the end user.
    
    `libgcc` seems to provide a method for this so we wouldn't need any
    extra dependency.
    
    Any thoughts on this or would it not be useful?
    
    Reviewers: austin, erikd, simonmar, bgamari
    
    Reviewed By: bgamari
    
    Subscribers: RyanGlScott, thomie, #ghc_windows_task_force
    
    Differential Revision: https://phabricator.haskell.org/D3027
    
    GHC Trac Issues: #13093, #13113


>---------------------------------------------------------------

f41c27d3ffdddbb1afe07de1bd25205061194c93
 rts/Linker.c        | 7 +++++--
 rts/linker/PEi386.c | 2 +-
 2 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/rts/Linker.c b/rts/Linker.c
index 9462bdb..8945a96 100644
--- a/rts/Linker.c
+++ b/rts/Linker.c
@@ -870,12 +870,11 @@ SymbolAddr* loadSymbol(SymbolName *lbl, RtsSymbolInfo *pinfo) {
 
     /* Symbol can be found during linking, but hasn't been relocated. Do so now.
         See Note [runtime-linker-phases] */
-    if (oc && oc->status == OBJECT_LOADED) {
+    if (oc && lbl && oc->status == OBJECT_LOADED) {
         oc->status = OBJECT_NEEDED;
         IF_DEBUG(linker, debugBelch("lookupSymbol: on-demand loading symbol '%s'\n", lbl));
         int r = ocTryLoad(oc);
         if (!r) {
-            errorBelch("Could not on-demand load symbol '%s'\n", lbl);
             return NULL;
         }
 
@@ -893,6 +892,10 @@ SymbolAddr* lookupSymbol( SymbolName* lbl )
 {
     ACQUIRE_LOCK(&linker_mutex);
     SymbolAddr* r = lookupSymbol_(lbl);
+    if (!r) {
+        errorBelch("^^ Could not load '%s', dependency unresolved. See top entry above.\n", lbl);
+        fflush(stderr);
+    }
     RELEASE_LOCK(&linker_mutex);
     return r;
 }
diff --git a/rts/linker/PEi386.c b/rts/linker/PEi386.c
index 824c821..f29bb8b 100644
--- a/rts/linker/PEi386.c
+++ b/rts/linker/PEi386.c
@@ -1326,7 +1326,7 @@ ocResolve_PEi386 ( ObjectCode* oc )
             S = (size_t) lookupSymbol_( (char*)symbol );
             if ((void*)S == NULL) {
 
-                errorBelch("%" PATH_FMT ": unknown symbol `%s'\n", oc->fileName, symbol);
+                errorBelch(" | %" PATH_FMT ": unknown symbol `%s'", oc->fileName, symbol);
                 return false;
             }
          }