Merge bitcoin/bitcoin#22409: configure: keep relative paths in debug info

0bc666b doc: add info for debugging with relative paths (S3RK)
a8b515c configure: keep relative paths in debug info (S3RK)

Pull request description:

  This is a follow-up for #20353 that fixes #21885

  It also adds a small section to assist debugging without absolute paths in debug info.

ACKs for top commit:
  kallewoof:
    Tested ACK 0bc666b
  Zero-1729:
    Light crACK 0bc666b

Tree-SHA512: d4b75183c3d3a0f59fe786841fb230581de87f6fe04cf7224e4b89c520d45513ba729d4ad8c0e62dd1dbaaa7a25741f04d036bc047f92842e76c9cc31ea47fb2

Author: fanquake

configure.ac

@@ -1661,8 +1661,8 @@ if test "x$use_ccache" != "xno"; then
   fi
   AC_MSG_RESULT($use_ccache)
   if test "x$use_ccache" = "xyes"; then
-    AX_CHECK_COMPILE_FLAG([-fdebug-prefix-map=A=B],[DEBUG_CXXFLAGS="$DEBUG_CXXFLAGS -fdebug-prefix-map=\$(abs_srcdir)=."],,[[$CXXFLAG_WERROR]])
-    AX_CHECK_PREPROC_FLAG([-fmacro-prefix-map=A=B],[DEBUG_CPPFLAGS="$DEBUG_CPPFLAGS -fmacro-prefix-map=\$(abs_srcdir)=."],,[[$CXXFLAG_WERROR]])
+    AX_CHECK_COMPILE_FLAG([-fdebug-prefix-map=A=B],[DEBUG_CXXFLAGS="$DEBUG_CXXFLAGS -fdebug-prefix-map=\$(abs_top_srcdir)=."],,[[$CXXFLAG_WERROR]])
+    AX_CHECK_PREPROC_FLAG([-fmacro-prefix-map=A=B],[DEBUG_CPPFLAGS="$DEBUG_CPPFLAGS -fmacro-prefix-map=\$(abs_top_srcdir)=."],,[[$CXXFLAG_WERROR]])
   fi
 fi
 

doc/developer-notes.md

@@ -12,6 +12,7 @@ Developer Notes
       - [Generating Documentation](#generating-documentation)
     - [Development tips and tricks](#development-tips-and-tricks)
         - [Compiling for debugging](#compiling-for-debugging)
+        - [Show sources in debugging](#show-sources-in-debugging)
         - [Compiling for gprof profiling](#compiling-for-gprof-profiling)
         - [`debug.log`](#debuglog)
         - [Signet, testnet, and regtest modes](#signet-testnet-and-regtest-modes)
@@ -253,6 +254,35 @@ Development tips and tricks
 Run configure with `--enable-debug` to add additional compiler flags that
 produce better debugging builds.
 
+### Show sources in debugging
+
+If you have ccache enabled, absolute paths are stripped from debug information
+with the -fdebug-prefix-map and -fmacro-prefix-map options (if supported by the
+compiler). This might break source file detection in case you move binaries
+after compilation, debug from the directory other than the project root or use
+an IDE that only supports absolute paths for debugging.
+
+There are a few possible fixes:
+
+1. Configure source file mapping.
+
+For `gdb` create or append to `.gdbinit` file:
+```
+set substitute-path ./src /path/to/project/root/src
+```
+
+For `lldb` create or append to `.lldbinit` file:
+```
+settings set target.source-map ./src /path/to/project/root/src
+```
+
+2. Add a symlink to the `./src` directory:
+```
+ln -s /path/to/project/root/src src
+```
+
+3. Use `debugedit` to modify debug information in the binary.
+
 ### Compiling for gprof profiling
 
 Run configure with the `--enable-gprof` option, then make.