I noticed on my Fedora 13 box that in the RPM macro %__global_cflags that -frecord-gcc-switches is missing, which is a nifty compiler feature that will record the flags passed to gcc in a section in the object file, thus aiding in the "how in the world was this compiled?" problem. An example:
[jstanley@hawtness ~]$ gcc -O2 -frecord-gcc-switches -g -o hello hello.c [jstanley@hawtness ~]$ readelf -p .GCC.command.line hello
String dump of section '.GCC.command.line': [ 0] hello.c [ 8] -mtune=generic [ 17] -g [ 1a] -O2 [ 1e] -frecord-gcc-switches
What do folks think about adding this as a default? Any reason not to (other than possibly a few bytes extra in the object files)?
On Sat, Oct 30, 2010 at 02:24:02AM -0400, Jon Stanley wrote:
I noticed on my Fedora 13 box that in the RPM macro %__global_cflags that -frecord-gcc-switches is missing, which is a nifty compiler feature that will record the flags passed to gcc in a section in the object file, thus aiding in the "how in the world was this compiled?" problem. An example:
[jstanley@hawtness ~]$ gcc -O2 -frecord-gcc-switches -g -o hello hello.c [jstanley@hawtness ~]$ readelf -p .GCC.command.line hello
String dump of section '.GCC.command.line': [ 0] hello.c [ 8] -mtune=generic [ 17] -g [ 1a] -O2 [ 1e] -frecord-gcc-switches
What do folks think about adding this as a default? Any reason not to (other than possibly a few bytes extra in the object files)?
+1
I think would also catch those cases where some gcc flag is found to break code generation. You reasonably see which binaries were affected.
Rich.
On 10/30/2010 06:01 AM, Richard W.M. Jones wrote:
On Sat, Oct 30, 2010 at 02:24:02AM -0400, Jon Stanley wrote:
I noticed on my Fedora 13 box that in the RPM macro %__global_cflags that -frecord-gcc-switches is missing, which is a nifty compiler feature that will record the flags passed to gcc in a section in the object file, thus aiding in the "how in the world was this compiled?" problem. An example:
[jstanley@hawtness ~]$ gcc -O2 -frecord-gcc-switches -g -o hello hello.c [jstanley@hawtness ~]$ readelf -p .GCC.command.line hello
String dump of section '.GCC.command.line': [ 0] hello.c [ 8] -mtune=generic [ 17] -g [ 1a] -O2 [ 1e] -frecord-gcc-switches
What do folks think about adding this as a default? Any reason not to (other than possibly a few bytes extra in the object files)?
+1
I think would also catch those cases where some gcc flag is found to break code generation. You reasonably see which binaries were affected.
I agree. Unless there is a notable performance cost in this, I say we should go for it.
~spot
On Mon, Nov 1, 2010 at 9:04 AM, Tom "spot" Callaway tcallawa@redhat.com wrote:
On 10/30/2010 06:01 AM, Richard W.M. Jones wrote:
On Sat, Oct 30, 2010 at 02:24:02AM -0400, Jon Stanley wrote:
I noticed on my Fedora 13 box that in the RPM macro %__global_cflags that -frecord-gcc-switches is missing, which is a nifty compiler feature that will record the flags passed to gcc in a section in the object file, thus aiding in the "how in the world was this compiled?" problem. An example:
[jstanley@hawtness ~]$ gcc -O2 -frecord-gcc-switches -g -o hello hello.c [jstanley@hawtness ~]$ readelf -p .GCC.command.line hello
String dump of section '.GCC.command.line': [ 0] hello.c [ 8] -mtune=generic [ 17] -g [ 1a] -O2 [ 1e] -frecord-gcc-switches
What do folks think about adding this as a default? Any reason not to (other than possibly a few bytes extra in the object files)?
+1
I think would also catch those cases where some gcc flag is found to break code generation. You reasonably see which binaries were affected.
I agree. Unless there is a notable performance cost in this, I say we should go for it.
How do you envision this working with debuginfo? Does this section get stripped out from normal install and collected into the -debuginfo subpackage, or does debuginfo need to be taught to leave this section intact in the actual installed binary?
josh
On Mon, Nov 01, 2010 at 09:04:12AM -0400, Tom "spot" Callaway wrote:
On 10/30/2010 06:01 AM, Richard W.M. Jones wrote:
On Sat, Oct 30, 2010 at 02:24:02AM -0400, Jon Stanley wrote:
I noticed on my Fedora 13 box that in the RPM macro %__global_cflags that -frecord-gcc-switches is missing, which is a nifty compiler feature that will record the flags passed to gcc in a section in the object file, thus aiding in the "how in the world was this compiled?" problem. An example:
[jstanley@hawtness ~]$ gcc -O2 -frecord-gcc-switches -g -o hello hello.c [jstanley@hawtness ~]$ readelf -p .GCC.command.line hello
String dump of section '.GCC.command.line': [ 0] hello.c [ 8] -mtune=generic [ 17] -g [ 1a] -O2 [ 1e] -frecord-gcc-switches
What do folks think about adding this as a default? Any reason not to (other than possibly a few bytes extra in the object files)?
+1
I think would also catch those cases where some gcc flag is found to break code generation. You reasonably see which binaries were affected.
I agree. Unless there is a notable performance cost in this, I say we should go for it.
-frecord-gcc-switches is unfortunately pretty much useless, see http://gcc.gnu.org/PR32998. Please don't add it, we want something actually usable, not this option.
Jakub
On Mon, Nov 1, 2010 at 9:12 AM, Jakub Jelinek jakub@redhat.com wrote:
-frecord-gcc-switches is unfortunately pretty much useless, see http://gcc.gnu.org/PR32998. Please don't add it, we want something actually usable, not this option.
Isn't it more useful in this state than not having the data at all? It seems that the bug that you refer to is about appending things to DW_AT_producer at this point, which is also useful, but I'm not convinced about that use of DW_AT_producer either, but that's another thread.
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